Simple Sensible Solutions

waltersgardens

The 7th edition of our Simple, Sensible, Solutions® guide. This color guide is packed with helpful information for green industry businesses who are growing and merchandising perennials.

TM

Simple, Sensible, Solutions ®

A GROWER’S GUIDE TO FINISHING PERENNIALS. 7TH EDITION.

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Table of Contents

Product Profile 3 - 5

Bare Root 6 - 9

Plug / Liners 10 - 13

Culture Guide 14 - 28

Grower’s Reference Chart 29 - 33

Plant Health 34 - 37

Summer / Early Fall Planting & Overwintering Recommendations 38 - 42

Additional Resources 43

Walters Gardens

Home of Proven Winners® Perennials

P.O. Box 137 • Zeeland, MI 49464 • Phone: 888-925-8377 • Fax: 800-752-1879 • Email: sales@waltersgardens.com

www.WaltersGardens.com • www.PerennialResource.com • www.ProvenWinners.com

Disclaimer of Liabilities: While every effort has been made to ensure the accuracy of the information provided in this growers guide, Walters Gardens, Inc. makes

no guarantee, express or implied, as to the procedures contained here. Walters Gardens, Inc. will not be liable for direct, indirect, incidental or consequential

damages in connection with or arising from the furnishing, performance, or use of this booklet.

© Walters Gardens, Inc. 2019

2 | Walters Gardens


Product Profile

Timing Chart

Product Size When to Plant Finish Size Average Finish Time

General Perennials #1 Grade Late Summer - Early Spring 1-gal 6-10 wks

#2 Grade Late Summer - Early Spring 1-gal 8-12 wks

#3 Grade Late Summer - Early Spring 1-qt 4-6 wks

20ct plugs Early Spring 1-gal 6-10 wks

30ct plugs

72ct plugs

128ct plugs

Early Spring

Spring

Late Summer

Early Spring

Spring

Late Summer

Early Spring

Spring

1-gal

1-qt

1-gal

1-qt

6-pk

1-gal

1-qt

6-pk

6-10 wks

4-6 wks

8-10 wks

4-6 wks

3-4 wks

12-16wks

5-8wks

4-5wks

Hibiscus #1 Grade Spring 3-gal 8-10 wks (flowers in 14-16 wks)

72ct plugs Spring 2-gal 10-12 wks (flowers in 14-16 wks)

Hosta 20ct plugs Midsummer - Early Spring

Late Summer

72ct plugs

Late Spring - Early Summer

Midsummer - Late Summer

Early Spring

1-gal

1-qt (Mini Hosta)

1-gal

1-qt

6-pk

8-10 wks

6-10 wks

16-20 wks

8-10 wks

6-8 wks

Succulents 72ct plugs Early Spring - Late Spring 1-qt 20-24 wks

Mangave 72ct plugs Early Summer 1-qt 10-14 wks

Tropicals 20ct plugs Early Spring

Early Spring

72ct plugs

Spring

Early Spring

1-gal

2-gal

4-in

1-gal

* Finish times vary by variety and growing environment (temperature, water, amount of light, fertilizer, etc.).

6-10 wks

10-12 wks

4-6 wks

8-10 wks

Based on zone 5, min

55-60ºF constant ghse temp

Based on zone 5, 65-70ºF or

warmer natural temps

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Product Profile

We’re Your Biggest Fan

We grade ahead of the curve

to give your daylilies more

fans and fuller containers.

Our Crowning Achievement

We’ve got our eyes on the

prize. Our goal is larger crowns

and more rewarding results.

The Root Cause

Our sandy fields promote fast

root growth to ensure that

what’s below matches what’s

above.

Bare Root

As the largest wholesale grower of bare root perennials in North America, we offer the widest selection of generously graded varieties. Most

are grown for one season and are sold as #1 grade transplants or divisions. Hemerocallis, Hosta, and select perennials that require it are grown

for two seasons in order to offer the best product. Our most popular varieties are offered in economically priced #2 and #3 grade divisions.

#1 Grade (G1)

Most #1 grade perennials are one year

plants or generously graded divisions of a

one year plant. #1 Grade Hemerocallis and

Hosta are sold as 3-5 eye/fan divisions of

a two year field clump depending on the

variety. Intersectional peonies are sold as

divisions of a two year field clump.

Count: sold in multiples of 25

Minimum order: 1 box of 25

4 | Walters Gardens

#2 Grade (G2) #3 Grade (G3)

Most #2 grade perennials are one year

plants or divisions of a one year plant. #2

Grade Hemerocallis and Hosta are sold as

smaller 2-3 eye/fan divisions of a two year

field clump.

Count: sold in multiples of 100

Minimum order: 1 box of 100

Select Hemerocallis and Hosta varieties

are sold as a #3 Grade division. These are

some of our most popular varieties offered

in an economical 1-3 eye/fan division of a

two year field clump.

Count: sold in multiples of 250

Minimum order: 1 box of 250


Product Profile

Plug Liners

Many of the products offered in this catalog are grown in plug form. Several sizes are available including 20, 30, 72, and 128 count. The

majority of our plugs are easy to transplant Elle Plugs, while others are traditional loose fill plugs. The type of plug used is based upon the

specific needs of the plant.

Larger 20 and 30ct plugs are best suited to customers looking for faster turnaround times and sales the same season. Smaller 72 and

128ct plugs are better suited for growers looking to produce larger quantities at a lower input cost. They are typically planted in summer

for sales the following spring.

We offer a number of perennials in economically priced 72 and 128ct plugs which are ideal for growers looking to produce larger quantities

of their best selling items at a lower input cost. Don’t see exactly what you’re looking for? We accept custom orders for 72s and 128s

(minimums apply). Please contact us for details.

Size Plug Measurements Minimum Order

20ct Elle Tray 31/4” deep x 23/4” wide 1 Tray of 20

20ct Deep Cell Tray 41/2” deep x 23/4” wide 1 Tray of 20

30ct Elle Tray 3” deep x 2” wide 1 Tray of 30

30ct Deep Cell Tray 41/4” deep x 2” wide 1 Tray of 30

72ct Elle Tray 21/2” deep x 11/3” wide 1 Tray of 72

128ct Elle Tray 2” deep x 11/8” wide 1 Tray of 128

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Bare Root

Walters Gardens is one of the largest field growers of perennials in the US, with over 1,500 acres dedicated to bare root production. In West

Michigan, we are blessed with sandy loam soil and moderate temperatures from our close proximity to Lake Michigan. Perennials thrive in

our fields, most reaching saleable size in just one growing season.

Our bare root perennial guide is meant to help you with the entire process of growing our perennials to finished size. To learn more about

our bare root sizes, see p. 4.

Roots

Fibrous Root

Taproot

Rhizome

Corm

A mass of profusely branched

roots, often with no main taproot.

Typically easy to divide.

Ex: Achillea, Veronica, Daylilies

The main descending root of a

plant, often with little branching.

Division is not recommended.

Ex: Gypsophila or Baptisia

A horizontal underground stem

with branching close to the soil

surface. Roots and shoots are

often produced along its length.

Ex: Siberian Iris

A solid, underground, bulb-like

portion of the stem of a plant

bearing roots at the base.

Ex: Crocosmia

Divisions

Eye

A bud or shoot atop the crown of a

plant from which foliage grows. Some

perennials that are graded by their

number of eyes include Paeonia,

Astilbe, and Hosta.

Fan

A fan refers to an individual unit of a

clump that includes one crown with

a set of leaves and roots attached.

Hemerocallis are typically graded by

their number of fans.

6 | Walters Gardens


Bare Root

Scheduling delivery of your bare root perennials

As a grower, you know that timing is everything. Sometimes it takes

a little experimenting to figure out what works best in your specific

climate. To help take the guesswork out of finishing your bare root

perennials, we offer you some guidelines in our timing chart on p. 3.

Be sure to keep in mind that finish times vary by variety and growing

environment.

As a general rule for many perennials, schedule delivery of your

spring order in time to allow 6-10 weeks of growing time for 1-gal

containers in a cool 50-60°F greenhouse. If plants will be grown

outdoors with no frost protection, schedule delivery after risk of hard

frost has passed as it is important to keep plants from freezing.

What to do when your plants arrive

Step 1: Open the Boxes

When your order arrives, it is important to open all of the boxes and

transplant all of the roots as soon as possible. Be sure to have plant

labels on hand when potting to ensure correct identification. If you

are not able to transplant the roots immediately, they may be stored

in a cool (35-40°F) area for a limited time.

Step 2: Inspect the Roots

When you open the boxes, check the condition of the bare root

plants. They should be firm, relatively dry, and typically are light

brown in color. Since some bare root plants may have been stored

in freezers where humidity is present, light surface mold may

appear on some roots. It is not harmful to the plant and typically

disappears once the boxes are opened and good air circulation is

provided. It is not necessary to spray them with fungicide or remove

the surface mold, though some customers prefer to do so.

If any roots are still frozen, allow them to thaw slowly in a cool (40-

50°F) room before handling. Do not put them immediately into a

warm greenhouse. If the roots are dry, soak them in a tub of water

containing a small amount of soluble fertilizer for one hour before

potting. This will help the plants get established more quickly.

If you are concerned about the condition of the plants in your

shipment, contact your sales representative or broker or Walters

Gardens, Inc. immediately so the issue can be resolved quickly.

Step 3: Determine Planting Order

The highest priority for transplanting bare root perennials should be

given to all evergreen types such as Iberis, Lavandula, and Phlox

subulata. Since their foliage is evergreen, these types of perennials

can dessicate more quickly if left exposed. Those perennials which

have thick, fleshy roots can typically be held over a bit longer before

planting. However, remember to pot up all of your bare root material

as soon as possible after receipt.

Step 4: When You’ve Finished Planting

We highly recommend that you apply a broad spectrum fungicide

drench at the time of transplant to prevent crown and root rots. This

is an important step that may take time now, but will save you time

and money in the long run. After the drench has been applied, move

the newly potted plants into a cool 50-60°F location with high light

levels. Leave them there until roots have been established, and then

raise the temperature slightly or move them to a warmer

greenhouse to encourage top growth.

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Bare Root

General Culture Guidelines for Bare Root Perennials

The cultural information presented here is intended to give you

general guidelines on how to grow bare root perennials. More

specific cultural guidelines for special categories of perennials can

be found on p. 22-28. In addition, a wealth of growing information is

available on our website, www.WaltersGardens.com. Cultural sheets

are provided for most genera, especially those that are more of a

challenge to grow. Direction to the Culture Sheets portion of our

website can be found under the Grower’s Corner section, or in the

tab at the bottom of an individual plant page.

Recommended Pot Sizes

#1 Grade Plants — Most finish best in 1-gal containers, though

some varieties such as Hibiscus are large enough to pot in 3-gal

containers.

#2 Grade Plants — Can be finished in 1-qt or trade 1-gal containers.

#3 Grade Plants — Can be finished in 1-qt or trade 1-gal containers.

Growing Media

We suggest potting up your new perennial liners in a well-drained

potting mix for optimum growth. A number of excellent bark or peatbased,

soilless commercial mixes are available. Aim for a soil pH

of 5.5-6.2 and an irrigation water pH of 5.4-7.0 for best results. For

moisture loving plants, use growing media with little to no bark that

will hold more moisture. Using a larger pot size will also keep the

plants from drying out so quickly.

Light and Temperature

For optimum rooting, most perennials should be planted in full sun.

For shade-loving plants such as ferns, hostas, Astilbe, and Dicentra,

50-70% shade is recommended.

When potting plants up in spring, be sure to keep the temperature

above freezing. Cold, wet conditions may cause plants to decline

or rot. Most perennials prefer to be grown at 50-55°F for 10-14 days

after potting to promote root growth and then grown at 55-60°F

until finished. Lower temperatures may be used to delay or suspend

growth, while warmer temperatures generally help to accelerate

growth.

Bare Root Perennials to Grow Cool: Achillea, Amsonia, Astilbe,

Artemesia, Baptisia, Clematis, Dicentra, Euphorbia, Irises, Lavandula,

Nepeta, Paeonia, Papaver, Phlox subulata, and Salvia. See the

Grower’s Reference Chart on p. 29 for a complete list.

Bare Root Perennials to Grow Warm: Coreopsis, Crocosmia,

Gypsophila, Hibiscus, Perovskia, Phlox paniculata, Rudbeckia, and

Yucca. See the Grower’s Reference Chart on p. 29 for a complete list.

Watering

After potting up your bare root plants, water them in thoroughly to

eliminate air pockets. Most bare root perennials benefit from being

kept on the drier side initially because they are unable to absorb

much moisture at this stage. The bare root plants need to develop

feeder roots, and keeping them dry forces them to seek moisture,

thereby initiating root growth.

It is best to water early in the day so that the foliage will have a

chance to dry out before the sun sets and the temperatures dip.

This will help to avoid foliar diseases.

Recommended

Planting Depth

Hemerocallis

(Daylily)

8 | Walters Gardens

Hosta

Allium

(Ornamental Onion)

Salvia

(Perennial Salvia)

Veronica

(Spike Speedwell)


Bare Root

When watering perennials with pubescent foliage, remember that

water tends to collect in the center of the plant, causing crown rot.

It is best to water pubescent and mildew-prone perennials early in

the morning so they have plenty of time to dry out during the day.

Monitoring Moisture Levels

Some bare root perennials prefer to be grown slightly dry. Plant

them in a very well-drained growing media, water them in, and

then water sparingly thereafter. Perennials that prefer to be grown

dry include: Amsonia, Artemisia, Euphorbia, Gypsophila, Iberis,

Lavandula, Nepeta, Penstemon, Perovskia, Platycodon, Salvia,

Sedum, and Yucca.

Other bare root perennials prefer to be grown with consistent

moisture levels. Their foliage tends to scorch and grow slowly if

they do not receive enough moisture. Grow these plants moist:

Astilbe, Dicentra, Hibiscus, Iris (Japanese, Louisiana, and Siberian),

Polygonatum, and Tradescantia.

Fertilizing

When bare root plants are first potted up, they are not able to

absorb fertilizer until they have established some feeder roots. Wait

to fertilize newly potted plants until they show some foliage growth,

approximately 4-6 inches for daylilies and other leafy perennials.

Once the bare root plants are actively growing, they can be

fertilized. Most growers use water soluble or slow release fertilizers

or a combination thereof. In general, most perennials benefit from

20-10-20 water soluble fertilizer at a rate of 50-150 ppm Nitrogen at

every watering.

To prevent salt build-up in the soil, avoid using slow-release fertilizer

in the soil until the weather begins to warm up in spring (around

April 1st in the north). Very little fertilizer is released before that

time when it is cold and cloudy. Always follow the manufacturer’s

recommendations when using fertilizer.

When potting up bare root plants in fall, do not use slow-release

fertilizer. Doing so will promote soft growth which could result in

severe die-back or death if exposed to freezing conditions.

When potting plants in spring, if you are using a slow release

fertilizer, it is best to incorporate it into the growing media at a rate

of 3/4 to 1 pound per cubic yard. Alternatively, you may top dress the

pots taking care not to apply the fertilizer directly to the crown of

the plants.

perennials, such as Hibiscus, prefer to have more space than others

when being grown to their finished size. In general, the more space

you can give plants to finish, the better their finished appearance

will be.

Air Circulation

Adequate air circulation is essential to avoiding disease issues when

growing perennials. This is especially important for mildew-prone

varieties such as Phlox paniculata and Pulmonaria. Be sure to

space plants well so the air has room to circulate around them. Use

fans or other ventilation if necessary.

Weed Control

We do our best to deliver clean, weed-free stock to our customers.

However, weeds are opportunists that will grow wherever they

possibly can. Some herbicides can be used successfully on certain

crops, but it is safest to pull weeds on a weekly basis before they

grow large and establish their roots.

Forcing Bare Root Perennials

Since most bare root material that is shipped from Walters Gardens,

Inc. in spring in a dormant state has already been vernalized, it can

be forced easily for sale anytime you’d like as long as the required

day length is met. Supplemental lighting may be required to

achieve satisfactory results. Alternatively, plants can be allowed

to come into flower naturally. The amount of time it takes to bring

plants into bloom varies widely by genus.

Plant Placement

The growing surface you select should have good drainage so that

plants never sit in water for an extended period. Landscape fabric

can be used for weed prevention. Be sure to space plants well

and use fans if necessary to provide good air circulation. Some

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Plugs / Liners

Of our wide selection of over 1,000 perennials, approximately half of our product line is offered in plug form. Depending on the needs of the plant,

it may be grown in an Elle Plug or a traditional loose fill plug tray. A full range of plug sizes, including 20, 30, 72, and 128 count trays, is available

to finish in your gallon, quart, or 6-pack sized containers. See timing chart on p. 3 for additional details.

Sizes

12”

11”

10”

9”

8”

7”

6”

5”

4”

3”

2”

1”

128ct Plug

(Elle)

72ct Plug

(Elle)

30ct Plug

(Elle)

30ct Plug

(Deep Cell)

20ct Plug

(Elle)

20ct Plug

(Deep Cell)

10 | Walters Gardens


Plugs / Liners

Scheduling delivery of your plug perennials

As a grower, you know that timing is everything. Sometimes it

takes a little experimenting to figure out what works best in your

specific climate. To help take the guesswork out of finishing your

plug perennials, we offer you some guidelines in our timing chart on

p. 3. Be sure to keep in mind that finish times vary by variety and

growing environment.

As a general rule for many perennials, schedule delivery of your spring

order in time to allow 6-10 weeks of growing time for 20 or 30ct plugs

finishing in 1-gal containers and 4-6 weeks for 72ct plugs finishing

in quarts (see timing chart on p. 3 for details.) If plants will be grown

outdoors with no frost protection, schedule delivery after risk of hard

frost has passed. It is important to keep plants from freezing.

What to do when your plants arrive

Step 1: Open the Boxes

When your plug order arrives, it is important to open all of the boxes

and transplant all of the plugs as soon as possible. Be sure to have

plant labels on hand when potting to ensure correct identification. If

you are not able to transplant the plugs immediately, they may be

stored in a cool area for a limited time.

Step 2: Inspect the Plugs

When you open the boxes, check the condition of the plugs.

Depending on the time of year and the variety, the plants may

be dormant or fully leafed out. If any plugs have frozen during

shipment, allow them to thaw slowly in a cool (40-50°F) room before

handling. Do not put them immediately into a warm greenhouse.

We strive to ship our plugs with sufficient moisture to last through

shipping. However, if any plugs appear dry they should be watered

immediately. Since all of our plugs contain a wetting agent in the

soil, they should re-wet easily.

If you are concerned about the condition of the plants in your

shipment, contact your sales representative or broker or Walters

Gardens immediately so the issue can be resolved quickly.

Step 3: Determine Planting Order

If there are both bare root and plug perennials included in your

perennial shipment, the highest priority for transplanting should be

the bare root varieties.

Once all of your bare root plants are potted up, you should begin

transplanting your plug perennials beginning with the smallest sized

plugs.

If you plan to hold over your plugs for a short period of time before

transplanting them, be sure to check them regularly to ensure they

are kept evenly moist. Never let the plugs dry out.

Step 4: When You’re Finished Planting

We highly recommend that you apply a broad spectrum fungicide

drench at the time of transplant to prevent crown and root rots.

This is an important step that may take time now, but will save you

time and money in the long run. After the drench has been applied,

move the newly potted plants into a cool 55-60°F location with high

light levels.Leave them there until roots have been established, and

then raise the temperature to 60-65°F or move them to a warmer

greenhouse to encourage top growth.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 11


Plugs / Liners

General Culture Guidelines for Plug Perennials

The cultural information presented here is intended to give you

general guidelines on how to grow plug perennials. More specific

cultural guidelines for special categories of perennials can be found

on p. 22-28.

In addition, a wealth of growing information is available on our

website, www.WaltersGardens.com. Cultural Sheets are provided for

most genera, especially those that are more of a challenge to grow.

Direction to the Culture Sheets portion of our website can be found

under the Grower’s Corner section, or in the tab at the bottom of an

individual plant page.

Recommended Pot Sizes

20 and 30ct Plugs — Most finish best in 1-gal containers, though

smaller varieties such as miniature hostas may work better in quarts.

72ct Plugs — Can be finished in trade 1-gal, 1-qt, or 6 pack containers.

Transplanting

When transplanting Elle Plugs, it is not necessary to remove the

paper sleeve since it will naturally degrade over time. The thinner

Elle Plug paper that is being used now degrades more quickly than

when the technology was new. However, some customers are more

comfortable removing the paper. This is acceptable only if it will not

harm the root structure of the plant.

As a general rule, perennials grown in traditional or Elle Plugs should

be potted up with the crown at the same soil level it was growing

in the plug. The Elle Plug paper should not stick up above the soil

surface after transplanted. Elle Plugs should be thoroughly watered

prior to transplanting.

Planting Depth

Most Plug Perennials,

such as the Hosta

pictured here, should be

planted even with the soil

level, or just a bit below

Growing Media

We suggest potting up your new perennial liners in a well-drained

potting mix for optimum growth. A number of excellent bark or peatbased,

soilless commercial mixes are available. Aim for a soil pH

of 5.5-6.2 and an irrigation water pH of 5.4-7.0 for best results. For

moisture loving plants, use growing media with little to no bark that

will hold more moisture. Using a larger pot size will also keep the

plants from drying out so quickly.

Light and Temperature

For optimum rooting, most perennials should be planted in full sun.

For shade-loving plants such as ferns and hostas, 50-70% shade is

recommended.

When potting plants up in spring, be sure to keep the temperature

above freezing. Cold, wet conditions may cause plants to decline

or rot. Most perennials prefer to be grown at 48-55°F for 10-14 days

after potting to promote root growth and then grown at 55-60°F

until finished. Lower temperatures may be used to delay or suspend

growth, while warmer temperatures generally help to accelerate

growth.

Plug Perennials to Grow Cool: Aquilegia, Brunnera, Delphinium,

Dicentra, Digitalis, Geranium, Grass-cool season, Helleborus,

Heuchera, Heucherella, Leucanthemum, and Lupinus. See the

Grower’s Reference Chart on p. 29 for a complete list.

Plug Perennials to Grow Warm: Buddleia, Campanula, Coreopsis,

Echinacea, Grasses-warm season, Gypsophila, Heliopsis, Perovskia,

Rudbeckia, non-hardy Succulents and Tropicals. See the Grower’s

Reference Chart on p. 29 for a complete list.

Watering

After potting up your plug perennials, water them in thoroughly to

eliminate air pockets. Initially, Elle Plug perennials benefit from extra

watering to help the plug absorb moisture. It is best to water early

in the day so that the foliage will have a chance to dry out before

the sun sets and the temperatures dip. This will help to avoid foliar

diseases.

When watering perennials with pubescent foliage, remember that

water tends to collect in the center of the plant, causing crown rot.

It is best to water pubescent and mildew-prone perennials early in

the morning so they have plenty of time to dry out during the day.

12 | Walters Gardens


Plugs / Liners

Once the plants are actively growing, they can be fertilized.

Most growers use water soluble or slow release fertilizers or a

combination thereof. In general, most perennials benefit from

20-10-20 water soluble fertilizer at a rate of 50-150 ppm Nitrogen at

every watering.To prevent salt build-up in the soil, avoid using slowrelease

fertilizer in the soil until the weather begins to warm up in

spring (around April 1st in the north). Very little fertilizer is released

before that time when it is cold and cloudy. Always follow the

manufacturer’s recommendations when using fertilizer.

When potting up plugs in fall, do not use slow-release fertilizer.

Doing so will promote soft growth which could result in severe dieback

or death if exposed to freezing conditions.

For the most

accurate snapshot

of a container’s

moisture level,

check the drainage

holes at it’s base.

Monitoring Moisture Levels

When growing perennials in a polyhouse, moisture levels can

vary depending on location and exposure. Areas that are prone to

drying out, such as those along sidewalks or near fans, should be

monitored closely. Perennials such as Dianthus and ornamental

grasses which prefer drier conditions would be good candidates for

such dry areas of the polyhouse.

Do not rely upon surface moisture to determine when it is time to

water. Instead, check the drain hole in the bottom of the container

for moisture. Most perennials prefer when the soil dries down a bit

between waterings.

Some plug perennials prefer to be grown slightly dry. Plant them in

a very well-drained growing media, water them in, and then water

sparingly thereafter. Grow these plants slightly dry: Aquilegia,

Asclepias tuberosa, Corydalis, Delosperma, Dianthus, Echinacea,

Epimedium, Gaillardia, Heuchera, Lupinus, Nepeta, Oenothera,

Perovskia, Stachys, Thymus, and Yucca. See the Grower’s Reference

Chart on p. 29 for a complete list.

Other plug perennials prefer to have consistent moisture levels.

Their foliage tends to scorch and grow slowly if they do not receive

enough moisture. Grow these plants moist: Cimicifuga, Dicentra

(except ‘Fire Island’ and ‘Pink Diamonds’), Galium, Ligularia, Lobelia,

Primula, Pulmonaria, Tiarella, and Trollius. See the Grower’s

Reference Chart on p. 29 for a complete list.

Fertilizing

When plugs are first potted up, they are not able to absorb fertilizer

until they have established some feeder roots. Wait to fertilize newly

potted plants until they show some foliage growth.

Plant Placement

The growing surface you select should have good drainage so that

plants never sit in water for an extended period.

Landscape fabric can be used for weed prevention. Be sure to space

plants well and use fans if necessary to provide good air circulation.

Some perennials, such as Hibiscus, prefer to have more space

than others when being grown to their finished size. In general, the

more space you can give plants to finish, the better their finished

appearance will be.

Air Circulation

Adequate air circulation is essential to avoiding disease issues when

growing perennials. This is especially important for mildew-prone

varieties such as Phlox paniculata and Pulmonaria. Be sure to space

plants well so the air has room to circulate around them. Use fans or

other ventilation if necessary.

Weed Control

We do our best to deliver clean, weed-free stock to our customers.

However, weeds are opportunists that will grow wherever they

possibly can. Some herbicides can be used successfully on certain

crops, but it is safest to pull weeds on a weekly basis before they

grow large and establish their roots.

Forcing Plug Perennials

When purchasing fresh material, plants should be bulked up and

vernalized over winter. Many perennials require vernalization to

bloom, while others may benefit from but not require vernalization.

Few do not require any vernalization to bloom. When receiving

plugs in spring from Walters Gardens, they will already have been

vernalized for the necessary amount of time in order to flower. Once

vernalized, plug perennials can be bulked and forced easily for

sale anytime you’d like as long as the required day length is met.

Alternatively, they can be allowed to come into flower naturally.

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Culture Guide

Five Recommendations for Growers

If you’re struggling with a certain crop or just starting out and need some good pointers, here are the top five things growers need to watch

for when finishing perennials.

1. Not all perennials are alike. If you plan to grow many different kinds of perennials, you’ll need multiple kinds of growing environments

in which to grow them. See p. 22-28 for cultural recommendations for specialized plants.

2. Many perennials benefit from planting the summer or fall prior to the season of sales. Often, you can start with a smaller plug and

yield bigger results by starting plants this way. See p. 38-39 for details.

3. Growing media is crucial. Know your soil and test it regularly for pH and EC levels. Choose the right growing media for each type of

perennial you are growing, whether it’s one that holds a lot of moisture for water loving plants or one that drains freely for those that

like it on the dry side.

4. Some top selling perennials with dark foliage, such as Hibiscus, need to be grown outdoors in order for the optimum color to be

developed. Creating the proper growing environment goes a long way towards growing the best quality finished perennials.

5. Many perennials, especially those that were started the summer or fall prior, can be forced into bloom for early spring sales. Keep in

mind however that most will require supplemental lighting and heat to force into bloom out of their natural cycle.

Watering Practices

Water quality is very important in perennial production. It is one of

the foundations of growing a quality crop of perennials. It is wise

to have your water source tested regularly for pH, salt levels, and

alkalinity. Perennials grow best when water is slightly acidic. You

may need to make adjustments to your water supply. If it is too

alkaline, you may need to inject acid into the water or use an acidic

fertilizer. If it is too acidic, you may need to inject a basic fertilizer.

When plants need water, it is best to water them well all the way

through the pots and then allow them to dry slightly between

irrigations. This will promote root growth to the bottom of the pots. If

plants are watered lightly but more frequently, they tend to produce

more surface roots and have a difficult time pushing roots to the

bottom of the pots. It is best to water your perennials early in the

morning to allow plenty of time for the foliage to dry before evening.

This will help to prevent disease issues such as root and crown rots.

An average growing media used for perennials contains a balanced

blend of peat, perlite, and bark. However, if you plan to use overhead

watering as the primary irrigation source, use a soil mix that is very

well-drained, containing a high concentration of bark and perlite and

less peat. An exception would be plants that require consistently

moist soil—those should be potted in a peat/perlite media with

minimal bark. When overhead watering, it is very important to

monitor pH and EC levels to ensure proper fertility since this practice

tends to leach fertilizer out of the soil.

Certain crops, especially those with pubescent leaves like Stachys

or Pulmonaria, perform better if drip or sub-irrigation is used. This

allows the foliage to stay dry and lessens the chances for rot. Be

sure to water such crops in the morning to allow plants to dry

thoroughly before nightfall.

When growing perennials that require consistent moisture in

outdoor growing facilities, it is important to monitor moisture levels

very closely. Such crops as Hibiscus may need to be watered

several times per day. Drip irrigation works best in situations like this

since it can be set on a timer or turned on any time of day without

getting the foliage wet, preventing foliar diseases.

14 | Walters Gardens


Culture Guide

Water by Number

Proper watering techniques can be difficult to teach to new

employees, especially when there is a language barrier. Tagawa

Greenhouse in Colorado developed a watering system that consists

of five levels from extremely dry (level 1) to wet (level 5) and is based

on visual and tactile clues for the worker. We have adapted their

system for our customers growing finished product, shown at right.

The primary watering range for most perennials is 2-4, meaning

they are watered up to a level 4 and allowed to dry down to a level

2 before they are watered again. Perennials that prefer drier soils

Levels

Level 1 - Extremely Dry

• Soil is light brown all the way through, dry to the touch, and separates easily from the edge of the pot.

• Soil will not stick together if pinched between fingers and may become hard and crumbly.

• Soil is difficult to re-wet even with a wetting agent.

• Plants may begin to wilt.

• Container is very lightweight.

Level 2 - Slightly Dry

• Soil is light brown at the top and slightly darker brown further down in the pot.

• Soil is fairly dry to the touch.

• Soil will stick together if pinched between fingers but falls apart easily.

• Container is lightweight.

are watered up to a level 3 and dried down to a level 2. Conversely,

perennials that prefer more moist soils are typically watered up to

a level 4 and dried down to a level 3. Few perennials can handle the

extremes of levels 1 and 5.

Below is a visual and descriptive account of each of the five

watering levels. We recommend that you adapt this system to your

own nursery, using your own plants, and post it in a prominent

location for your workers to reference on a regular basis.

Level 3 - Average

• Soil is medium brown most of the way through the pot but darker brown at the very bottom.

• Soil is slightly damp to the touch.

• Soil will stick together if pinched between fingers.

• Pots around the edges of the crop block dry out quicker and should be monitored for moisture.

• Container is of moderate weight but does not drip water.

Level 4 - Moist

• Soil is dark brown all the way through the pot.

• Soil feels moist to the touch.

• Some water can be squeezed from the pot.

• Container is slightly heavy but does not drip much water.

Level 5 - Wet

• Soil is dark brown to black all the way through the pot because it is fully saturated.

• Soil feels wet to the touch.

• Water drips from the pot when you pick it up.

• Container is very heavy and drips a lot of water.

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Culture Guide

Onsite Soil Testing

In addition to water quality, onsite soil testing is one of the

foundations of growing a quality crop of perennials. Surprisingly,

it is often overlooked by growers. Investing in onsite soil testing

is well worth the effort and minimal expense as it helps to prevent

nutritional deficiencies and grow more vigorous, healthier, pest and

disease resistant crops. We recommend that you invest in a good

quality pH/EC soil testing kit. They are readily available online for

approximately $200-$300.

There are several methods of testing soil, but the one we

recommend is called the pour thru method. You will notice the EC

rates given in this guide specify they are using this method. You will

also find recommended pH and EC rates on our cultural sheets on

www.WaltersGardens.com

There are seven basic steps to testing soil for pH and EC levels

using the pour through method, as defined by North Carolina State

University’s Floriculture Research department.

1. Irrigate the plants you are going to test one hour before testing

begins. Make sure the growing media is completely saturated.

2. Put a saucer or something to catch the water under the pots right

before you start the test.

3. Pour enough distilled water on the potted plants to get 50ml of

leachate (the water that drains through the container). For a one

gallon pot, this is typically 150ml of distilled water. Water must be

distilled or deionized to obtain accurate readings.

4. Collect the leachate in a clean container so you can measure its

pH and EC.

5. Before testing the leachate, calibrate your pH and EC meters.

Skipping this step may lead to inaccurate readings.

6. Measure the pH and EC of your samples as soon as possible after

they are collected.

7. Make adjustments to the pH and EC levels of your soil as needed.

NC State University is an excellent source of information about soil

testing. Visit their website: www.ces.ncsu.edu/depts/hort/floriculture

Tips for Successful PGR Applications

Some perennials benefit from applications of growth regulators to

ensure the highest quality crop. While ideal growing conditions and

spacing go a long way to improve quality, it is not always possible

to have the best environment for every crop and some plants that

are naturally quite tall can benefit from PGR applications even when

grown in the very best possible situation. Here are some tips on

applying growth regulators and rate suggestions for starting with

on the genera that you might find needing some control on a more

frequent basis. Keep in mind that these rates are just suggestions,

and will vary based on your regional location, environment and even

the water quality in your operation.

• Apply foliar PGR applications early in the morning (or on a cloudy

day) for best results – this allows them to dry the slowest and

gives the most uptake. If in a greenhouse with retractable shade

curtains, you can also pull the shade on a sunny day in a pinch.

You can increase uptake by running a LIGHT MIST of water over

the crop when it is almost dry from the application – not enough

to rinse the chemical off, just enough to rewet the foliage.

• Uniconazole (Sumagic/Concise) and Paclobutrazol (Bonzi/Piccolo)

require stem contact for best absorption.

• Familiarize yourself with the labels, and make sure to use a

surfactant if suggested on the label – for example, Configure has

the best efficacy if applied with a surfactant. Capsil is a good

example, the rate typically used with Capsil is 6oz/100gals. Apply

volumes based on label suggestions. Some PGRs require only a

light spray (ie. Cycocel) whereas others require a heavier spray.

• Some PGRs (Dikegulac Sodium, Fascination/Fresco, Cycocel,

Florel) may cause either yellowing or a halo – this is normal and

plants will outgrow it.

• When drenching, try to apply when soil has been allowed to dry

slightly so you get the most uptake of the chemical, and then be

careful not to apply so much water as to leach the chemical out

for the 7-10 days.

• Everyone has their own method, but the “safest” way (and often

the best results) is to layer lighter spray applications on as

needed rather than a one-time punch of a drench or higher rate

spray.

• There is a lot of good information out there (less so on

perennials, but getting better!). A great resource is the annually

published Grower Talks PGR guide – one on annuals, one on

perennials. Start there and make adjustments as needed based

on your crop and growing conditions.

16 | Walters Gardens


Plant Growth Regulator (PGR) Recommendations

Genus

Hardy Perennials

Plant Growth

Regulator (PGR)

Rate

Achillea Daminozoide 2500 ppm

Daminozide + Uniconazole

Uniconazole

Configure

2000 + 3 ppm

7-15 ppm

2500-5000 ppm

Agastache Daminozide 2500-5000 ppm

Daminozide + Chlormequat

Chloride

Paclobutrazol

Uniconazole

Configure

2500-5000 + 1000-1500

ppm

30-60 ppm

5-10 ppm

300-500 ppm

Alcea Paclobutrazol 5-15 ppm

Paclobutrazol

Uniconazole

3-6 ppm drench

2.5-5 ppm

Amsonia Paclobutrazol 15 ppm

Uniconazole

Uniconazole

5-10 ppm

1 ppm drench

Anemone Daminozide + Uniconazole 2000 + 3 ppm

Aquilegia Daminozide 1500-2500 ppm

Daminozide + Uniconazole

Uniconazole

1875 + 3 ppm

5-15 ppm

Arabis Daminozide 2500 ppm

Notes

Culture Guide

PGRs may need to be applied multiple times to get good

control.

Apply PGRs as sprays early, before elongation has

occurred. If elongation has already occurred, best

control is through the Paclobutrazol drench.

Apply just as flower stems are beginning to elongate.

Not required on some varieties.

Artemisia Daminozide 5000 ppm Growing cool and dry will reduce the need for PGR.

Daminozide + Chlormequat

Chloride

Paclobutrazol

5000 + 1500 ppm

40-50 ppm

Aruncus Uniconazole 5 ppm

Asclepias Daminozide 3750-5000 ppm

Uniconazole

5-10 ppm

Aster Daminozide 2500-5000 ppm Make first application 5-7 days after pinching.

Paclobutrazol

30-50 ppm

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Culture Guide

Plant Growth Regulator (PGR) Recommendations

Genus

18 | Walters Gardens

Plant Growth

Regulator (PGR)

Rate

Astilbe Daminozide 2500-5000 ppm Apply PGR when flower stem appears above foliage.

Daminozide + Uniconazole

Paclobutrazol

Uniconazole

2000 + 3 ppm

15-30 ppm

5-10 ppm

Baptisia Paclobutrazol 6-10 ppm drench

Uniconazole

Uniconazole

1 ppm drench

5-15 ppm

Notes

Growing cool is the best height control. Make first PGR

applications early in the crop, when shoots are just a few

inches tall.

Brunnera Daminozide 2500 ppm If toning is required, often not needed.

Uniconazole

5 ppm

Buddleia Paclobutrazol 6 ppm drench Begin PGR applications 1-2 weeks after pinching.

Uniconazole

5-15 ppm

Campanula Daminozide 2500-3750 ppm

Paclobutrazol

Uniconazole

10-30 ppm

2-5 ppm

Clematis (Herbaceous) Uniconazole 5-10 ppm

Coreopsis Daminozide 2500-5000 ppm

Daminozide + Uniconazole

Uniconazole

2000 + 3 ppm

5-10 ppm

Apply just as flower stems are beginning to elongate.

Compact varieties will need little to no PGR, start on

these with 2500 ppm Daminozide.

Delphinium Paclobutrazol 30 ppm Apply when flower stems grow above foliage.

Uniconazole

5 ppm

Dianthus Daminozide + Uniconazole 2000 + 3 ppm Typically not needed if grown cool.

Dicentra Daminozide 2500 ppm

Digitalis Ancimidol 25 ppm

Daminozide

Uniconazole

2500 ppm

5 ppm

Echinacea Daminozide 2500 ppm

Daminozide + Uniconazole

Uniconazole

Uniconazole

2000-2500 + 3-5 ppm

5 ppm

1 ppm drench

Euphorbia Flurprimidol 45 ppm

Paclobutrazol

Uniconazole

30 ppm

5 ppm


Plant Growth Regulator (PGR) Recommendations

Genus

Plant Growth

Regulator (PGR)

Rate

Gaillardia Daminozide 2500-5000

Daminozide + Chlormequat

Chloride

Daminozide + Paclobutrazol

Daminozide + Uniconazole

2500-3750 + 1000 ppm

2500-3750 + 15 ppm

2000-2500 + 3-5 ppm

Gaura Daminozide 2500 ppm

Uniconazole

5 ppm

Geranium Daminozide + Uniconazole 2000 + 3 ppm

Uniconazole

5 ppm

Notes

Culture Guide

Geum Paclobutrazol 30 ppm Apply as flower stems grow above foliage.

Uniconazole

5 ppm

Heliopsis Daminozide 2500 ppm

Uniconazole

5-10 ppm

Hemerocallis Uniconazole 1 ppm drench

Heuchera Uniconazole 5-10 ppm Typically not needed if grown under ideal conditions.

Heucherella Uniconazole 5-10 ppm Typically not needed if grown under ideal conditions.

Hibiscus

Daminozide + Chlormequat

Chloride

Uniconazole

Paclobutrazol

3750 + 1000 ppm Apply PGRs about 5 days after a pinch.

2.5-15 ppm

1 ppm drench

Hosta Daminozide 2500 ppm

Uniconazole

Uniconazole

5 ppm

1 ppm drench

Iberis Paclobutrazol 15 ppm

Uniconazole

2.5 ppm

Knautia Daminozide 2500 ppm

Paclobutrazol

Uniconazole

30 ppm

5 ppm

Kniphofia Paclobutrazol 30-45 ppm

Uniconazole

5-7.5 ppm

Lavandula Uniconazole 5 ppm

Leucanthemum Uniconazole 5-7.5 ppm

Liatris Uniconazole 5.10 ppm

Be aware of what size class of hosta you are growing.

Mini, small, and unvernalized hosta will not typically

need any PGR.

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Culture Guide

Plant Growth Regulator (PGR) Recommendations

Genus

Plant Growth

Regulator (PGR)

Rate

Lobelia Ancimidol 25 ppm

Daminozide

Uniconazole

2500 ppm

5 ppm

Lupinus Daminozide 2500 ppm

Daminozide + Uniconazole

Paclobutrazol

2000 + 3 ppm

20 ppm

Malva Paclobutrazol 15 ppm

Uniconazole

2.5 ppm

Monarda Daminozide + Uniconazole 2000 + 3 ppm

Nepeta Paclobutrazol 30 ppm

Uniconazole

5 ppm

Oenothera Uniconazole 5-10 ppm

Papaver Daminozide 2500 ppm

Penstemon Daminozide 2500 ppm

Uniconazole

5-10 ppm

Perovskia Daminozide 2500 ppm

Daminozide + Uniconazole

Uniconazole

2000 + 3 ppm

5-10 ppm

Phlox (Tall Garden) Paclobutrazol 45 ppm

Uniconazole

10 ppm

Platycodon Daminozide 2500 ppm

Uniconazole

5 ppm

Rudbeckia Daminozide 2000 ppm

Uniconazole

3 ppm

Salvia Daminozide 2500 ppm

Uniconazole

5-10 ppm

Scabiosa Daminozide 2500 ppm

Paclobutrazol

Uniconazole

30 ppm

5 ppm

Sedum Daminozide 2500-5000 ppm

Paclobutrazol

Uniconazole

20-30 ppm

5-10 ppm

Spigelia Uniconazole 5-10 ppm PGR not typically needed if grown under ideal conditions.

Stokesia

Daminozide + Chlormequat

Chloride

2000 + 1000 ppm

Notes

20 | Walters Gardens


Plant Growth Regulator (PGR) Recommendations

Genus

Plant Growth

Regulator (PGR)

Rate

Notes

Tiarella Uniconazole 5 ppm Typically not needed.

Tradescantia

Veronica Uniconazole 5-10 ppm

Viola Daminozide 2500 ppm

Grasses & Sedges

Best growth control is growing in cool temperatures.

Calamagrostis Flurprimidol 10 ppm Make first application when plants are 6-12" tall.

Paclobutrazol

Uniconazole

10 ppm

1 ppm drench

Miscanthus Flurprimidol 10 ppm

Paclobutrazol

Uniconazole

10 ppm

2 ppm

Panicum Flurprimidol 10 ppm

Paclobutrazol

Uniconazole

10 ppm

2 ppm

Pennisetum Flurprimidol 10 ppm

Tropicals

Paclobutrazol

Uniconazole

10 ppm

2 ppm

Digiplexis Uniconazole 10 ppm Apply PGRs just as flower spikes are starting to elongate.

Uniconazole

1 ppm drench

Culture Guide

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Culture Guide

Culture Recommendations for Specialized Plants

Astilbe

Plant in 1-gal containers with the eyes just at or slightly below the

soil surface.

Begin growing plants cool at 50-55°F for the first 10-14 days. After

that, increase the temperature to 55-60°F to speed flowering or

lower temperature to delay flowering.

The most critical growing factor for Astilbe is water. Increase

watering as the foliage emerges and plumes mature. Plants should

never be allowed to dry out. If the margins of the leaves turn brown

and crispy, the plants are not being kept moist enough. Avoid

watering after mid-afternoon.

Astilbes are moderate feeders. We recommend a constant liquid

feed of 50-100ppm N.

Because they are sensitive to high salts, the plants may experience

root injury and become scorched if the soluble salt levels are

allowed to build up. We recommend an EC of 1.5-2.0 using the pour

through method.

• Use mouse bait when overwintering.

• Plants should be shaded during periods of high light intensity.

A 55% shade cloth is recommended in the north when

temperatures reach 65-70°F. A heavier 70% shade cloth will be

necessary in the south.

Baptisia (False Indigo)

The big concern with bare root Baptisia is that the roots will dry out

since dry roots are almost always connected to poor performance.

Fortunately, there are a few quick and easy steps that can be taken

to ensure success in growing.

First, plant your bare root Baptisia as soon as possible into a

true 1-Gallon container or larger. If the roots are too large for the

container you can trim them slightly right before potting.

Planting depth is very important. The eyes should be planted right at

the soil line so the crown is completely submerged. If the crown sits

above the soil the roots will become significantly drier than if the

crown is below and result in poorer performance.

Due to the dense nature of the root system there is a probability

that air gaps will form below the crown and surrounding roots when

planting from bare root. Taking care to fill in between the roots when

planting, as well as a thorough watering after planting will solve this

concern.

A porous peat based growing media or well drained bark are usually

good choices.

Despite heavy concerns over dry roots, Baptisias are not a thirsty

plant. Once the roots are established, they require only low to

moderate watering.

Start cool at 55-60°F and provide high light levels with good air

movement.

Pinching is not necessary and has a good chance of removing or

damaging the emerging flowers. Baptisia are vigorous growers,

drenching with Bonzi at 6” tall will effectively control plant height.

Planting Depth

Baptisia plugs should be

about 1/2” below the soil

line. This will promote

better eye development

and more stems the

following year.

Clematis (Herbaceous, non-Vining)

When most people think of Clematis they are usually thinking of

the vining types, but bush Clematis are much easier to control in

containers than their vining counterparts and have unique, bellshaped

flowers that lend a very different look to the garden.

Bush Clematis, or herbaceous

clematis, are offered as bare root

inputs and should be planted

with the crown slightly below the

soil line in late winter to spring.

The bare root material will have

received a vernalization in the

fields, so no additional cold

treatment is needed.

In the landscape, bush Clematis

benefits from either some

perennial neighbors or an

obelisk to help support the foliage. Likewise in containers, a trellis

will help to maintain the upright form.

High light levels will help to grow the highest quality plants.

22 | Walters Gardens


Culture Guide

Echinacea (Coneflower)

Walters Gardens begins to ship vegetatively propagated, actively

growing Echinaceas in the beginning of April. Prior to April 1st,

Echinacea are shipped in either a dormant or newly emerging state.

If you do not have a heated greenhouse in which to keep them

actively growing, schedule your delivery later in spring when night

temperatures average 50-60°F and daytime temperatures average

65-70°F.

• High light intensities are required for best growth.

• Echinaceas flower best under 14 hour days or a four hour night

interruption between 10PM and 2AM.

• Best performance comes in well-drained soil of moderate

to slightly dry moisture. Allow the soil to dry down between

waterings for best root growth.

• Echinacea will become stunted and lack overall vigor if fertilizer

and EC levels are too high. Use slightly acidic soil with an EC of

1.5-2.0 using the pour through method for best results.

Helleborus (Lenten Rose)

Hellebores are a long crop, but worth the wait. We offer several

different plug inputs that can be utilized at varying time of year.

• 128ct plugs are the smallest and should be planted in late winter

to early spring in the south, or early summer in northern regions,

and can be sold green later the same season or overwintered

for the following spring’s sales. Expect only 10-15% flowering

that following spring, since they will have received only one

vernalization.

• 30ct plugs are a larger input and should be planted in late winter

to early spring in the south, and in the late winter in the north.

Follow similar timing as for the 128s, selling green plants later

that summer or lightly flowering plants the following spring.

• 20ct plugs are the largest plug size we offer and are available in

both the fall and the spring. Fall planted 20cts bulk and develop

roots well at that time of year since hellebore actively grow

during the cooler months, and then will bloom at about 80%

capacity the following spring. Spring planted 20cts have already

received a second vernalization in the plug, so can be planted

and sold the same season at about 80% flowering capacity.

Hellebores are cold weather plants which are actively growing

from late winter through spring. They stop growing in summer but

resume growth again in the fall. Plants in production through the

summer should be pushed tightly together to help maintain a cooler

environment around the roots. Reflective aluminum shade cloth

also helps to keep plants cooler during the summer months.

When plants are actively growing, fertilize moderately with 100-

150ppm N at every irrigation. Reduce to 75-150ppm N at every other

irrigation in summer and mid-winter.

Use a bark-based growing media with a slightly acidic pH of 5.8-6.4.

In production, Hellebores prefer average moisture, and should be

allowed to dry only slightly between waterings. In the garden, they

are quite drought tolerant.

Use a 50-75% shade cloth for this shade perennial during the

summer months.

Vernalization is required for flowering. Plants that are produced from

tissue culture bloom about 85% after one vernalization compared to

those produced from seed which bloom about 10-15%. All plants will

bloom after the second vernalization. After the potted plants have

been bulked up from spring through fall, vernalize them for up to

8-10 weeks at 35-40°F and keep them cold until you want them to

flower. Flowering often begins even in unheated greenhouses in the

late winter, especially when temperatures are above 35°F.

Hemerocallis (Daylilies)

Daylilies are one of the most widely

recognized perennials, are deer and

rabbit resistant, and are very

versatile in the landscape.

Hardy from zones 3 to 9, they

can be used throughout a wide

range of garden conditions.

Our daylilies are all grown in

our bare root fields and roots

are trimmed before shipping.

Root pruning is preferable to

cramming the roots into a pot, and

will not result in any setback in

growth. In many cases trimming will

actually accelerate rooting in.

Bare root divisions should be planted in

well-drained media and watered in thoroughly.

Hemerocallis prefer even moisture until established, but then can

be allowed to dry down slightly between irrigations until bud set, at

which point returning to consistent moisture application will improve

flower quality.

For the first few weeks after planting, daylilies do not require

fertilizer. Once actively growing they are moderate feeders and will

perform best under a constant liquid feed program of 75-125 ppm N.

Too much fertilizer will encourage soft, weak growth.

Late summer planting will result in bigger plants and more flowers.

Allow at least 6-8 weeks to establish roots before temperatures

drop consistently below freezing, and do not fertilize at this time.

When overwintering, trim plants to 2 inches as late in the season as

possible, as trimming too early will result in unwanted regrowth.

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Culture Guide

Hibiscus (Culture for Spring Planting)

• Pot up bare root Hibiscus immediately upon arrival.

• Grow Hibiscus in full sun at 68°F or warmer constant

temperature. Bare root plants can be grown colder outdoors.

• Grow cultivars with purple foliage outdoors to achieve proper

coloration.

• Pinch top growth back once to 3-5 nodes.

• Drench each pot with 1ppm Sumagic® one week after pinching.

• Keep plants moist at all times to prevent flower buds from

aborting.

• Feed with 150-200ppm N to ensure vigorous growth. Maintain EC

levels of 2.5-3.5 using the pour thru method.

• Watch for aphids, whiteflies, mites, and sawfly larvae.

Hostas

Growing Hostas in Early Spring

It is quite normal for different hosta varieties to re-emerge at

significantly different rates in spring. Some will virtually explode

from the soil while others are slower to emerge. The speed of

emergence can depend on:

• Growing Temperature: Hostas grown in a cool 40-50°F

environment can take much longer to emerge than plants grown

at 60-70°F. However, if you flush them out too quickly, the leaf

substance will be thinner, so it is better to reemerge them in cool

temperatures.

• Length of Vernalization: Many hostas require a full 10 week

vernalization (35°F temperatures) to grow properly the following

spring. Hostas that do not receive the necessary cold treatment will

take significantly longer to reemerge. Hostas received from Walters

Gardens, Inc. in early spring will be dormant vernalized plants.

• Cultivar/Species: Generally, tokudama and fortunei types emerge

much slower than those with undulata, sieboldiana, plantaginea,

and montana parentage. Long days are required for hostas to

bulk up their foliage and root systems.

General Recommendations for Hostas

We strongly recommend that you pot up

your plug and bare root hostas the summer

prior to sale. Such hostas will develop more

eyes, a better root system, and more mature

traits including proper variegation. They also

will be saleable quicker in spring and have a

much higher perceived value.

• Pot up plants in a well-drained, bark-based,

soilless mix with the eyes at or just below the

soil surface.

• When transplanting in spring, keep

hostas at 50°F for the first two

weeks to promote root growth.

Minimum temperatures may then

be lowered to 40°F.

• Keep soil moist early in the growing

season without overwatering. Later in

the season, allow soil to dry slightly

between waterings. Dormant hostas

require very little water.

• Hostas will benefit from a light

application of liquid fertilizer (20-10-

20 with 50ppm Nitrogen) in early

spring. Since it is critical to keep all

granular fertilizers out of the crown

Walters Gardens has a

zero tolerance policy for

Hosta Virus X (HVX), and

tests regularly for the virus

to avoid injury, liquid feed is safest. Alternatively, a top dressing

of slow release fertilizer may be used. Roots will rot if too much

fertilizer is applied. Aim for an EC rate of 1.5-2.0 using the pour

through method. In the fall, only a light fertilizer application, if

any, is necessary. Apply very little Nitrogen in the fall to allow

plants to go dormant.

• The use of a 50% shade cloth in the north (70% in the south)

is recommended since excessive light may cause irregular

bleached areas (sun scald) on the leaves of sensitive varieties.

Shading will also help blue hostas retain their attractive blue

color later into the season.

Lagerstroemia

• Lagerstroemia, commonly called Crapemyrtles, are traditionally

a southern plant but because of advances in their genetics some

varieties are now hardy to Zone 6. 30ct plugs can be planted

in spring through summer, and will finish in 12-14 weeks in a

premium 2 gallon container.

• Suggested container size is 2-3 gallons.

• Due to their southern heritage, Crapemyrtles are a heat loving

plant and will put on the most growth in the heat of the summer.

24 | Walters Gardens


Culture Guide

When planting in the greenhouse in spring, you will want to

maintain temperatures of at least 68-70°F.

• Crapemyrtles grow best under high light levels and in a welldrained

media with a pH of 5.5-6.

• They are moderate feeders, taking a constant liquid feed of 100-

125ppm Nitrogen.

• Crapemyrtles bloom in August on new growth and will die back

to the ground over winter in the north.

Lavandula (Lavender)

Lavender is trending right now due to its multiple uses as an

ornamental perennial, culinary herb and fantastic aromatic foliage.

Three input sizes of lavender are available to purchase from Walters

Gardens:

• 30ct plugs should be planted in late winter to spring and will fill a

trade gallon in 7-9 weeks.

• 72ct plugs may be planted either in the late summer and sold

the following spring, or in late winter to spring, filling a trade

gallon container in 8-12 weeks depending on the season.

• Bare root lavender is best planted in late winter to spring in

1-2 gallon containers, and finishes in 8-10 weeks. The foliage

is shaped by us, enabling you to finish an attractive plant with

no trimming required on your part. When receiving bare root

lavender, we recommend that it be one of the first things you

get out of the box and plant, and water in immediately and

thoroughly to eliminate air pockets in the media and to hydrate

the plants. It is also beneficial to cover bare root lavender with

remay cloth after planting to prevent the dormant evergreen

foliage from dessication, until new roots form and can support

the new growth.

Most lavender requires 8-10 weeks of vernalization in order to flower,

with the exception of SWEET ROMANCE®, which is cold beneficial

but will flower without vernalization. All bare root lavender will have

received the necessary cold treatment in the field.

Lavender will perform best when planted in a well-drained mix and

grown with moderate moisture to slightly dry. Do not grow too dry

(do not allow to wilt) or too wet, as both extremes may lead to root

rots. Avoid high humidity and overhead watering late in the day to

minimize foliar issues.

Fertilizer levels for lavender should be fairly low, in the 50-75 ppm N

range when using constant liquid feed, as they are light feeders.

Rhizoctonia, Phytopthora, Botrytis and other fungal pathogens

can be problematic if grown under less than ideal conditions. A

preventative drench after transplant and preventative sprays will

help keep pathogens at bay.

Lupines

Lupines can be grown from larger 30ct plugs in spring or smaller

72ct plugs the fall before sales. If planting in spring, grow them cool

at 60-65°F constant temperatures. If growing in fall, keep plants

above 50°F until they are finished and then vernalize them for 6-8

weeks or longer in a minimally heated greenhouse or unheated cold

frame.

• Use a well-drained, bark based growing media with a pH of 5.8-

6.2 to ensure proper drainage. Maintain average to moist soil

moisture.

• Lupines are light to moderate feeders. Fertilize with a constant

liquid feed of 75-100ppm N at every irrigation and aim for an EC

rate of 2.0-2.5 using the pour through method.

• PGRs may be used to control the height of the foliage and flower

stalks.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 25


Culture Guide

Soil Level

11/2-2” Planting Depth

Eyes

Peonies

Garden Peony

Eyes

Crown

Intersectional Peony

Garden Peonies

The most critical aspect of growing peonies is their planting depth.

For garden peonies, the eyes on the root should be planted to a

depth of 11/2-2 inches below the soil surface. The lower roots may

be trimmed to fit the pot if necessary. Proper planting will help to

ensure a good flowering performance.

Intersectional Peonies

For intersectional peonies, the crown should be planted 11/2-2 inches

below soil level. If the eyes have already begun to grow, they may

stick up above the soil a bit after planting the crown below soil level.

General Cultural Recommendations for Peonies

When you receive your shipment of peonies, open the boxes and

inspect the roots. If they look dry, soak them in water for 12 hours

or overnight before planting. If you are not able to plant them right

away, repack them in the materials in which they were shipped and

store them in 38-42°F temperatures for up to 10 days.

• 2/3 eye divisions should be potted in 1 gallon containers.

• 3/5 eye divisions should be potted in 2-3 gallon containers.

• Use a well-drained, bark-based, commercial growing mix with a

pH of 6.5-7.0. Peonies need good drainage and air circulation for

disease control.

Planting peonies in the fall will result in improved flowering the

following spring. Fall planting is highly recommended.

If planting peonies in the spring, it is important to grow them cool

in order to yield stronger plants and prevent them from growing too

fast. We recommend 45-50°F days and cold nights of 35-40°F. It

may become necessary to run the fans in the greenhouse on sunny

days to maintain this cool temperature. When grown at higher

temperatures, the plants slow their bud development, the flowers

age faster, and leaf curl may occur.

In the spring, use a low rate fertilizer such as 18-6-8 at 100-150ppm

at every other watering. Over-fertilization can inhibit flowering. Aim

for an EC rate of 1.5-2.5 using the pour through method.

Perovskia

• Bare Root Perovskia are best planted in Spring. They should be

potted in a 1-Gal container and kept at 68-72°F to finish in 6-8

weeks.

• Perovskia grown from plugs finish in a 1-Gal container as well but

will finish in 10-12 weeks. We recommend plug Perovskia as a

late summer planting to overwinter.

• Vernalization is beneficial to bloom but not necessary.

• We recommend 75-100ppm Nitrogen in a constant liquid feed but

if you prefer slow release fertilizers we recommend a rate of 1.0-

1.25 lbs. per cubic yard of growing media.

• The EC rate is 1.5-2.0 using the pour through method.

• In the landscape, Perovskia are drought tolerant. In production,

we recommend keeping your plants moderately moist to slightly

dry with either drip or overhead irrigation.

• Grow this crop under clear plastic or indoors or in direct sunlight.

Proper lighting will keep the plant more compact.

• Perovskia overwinter best in a minimally heated greenhouse.

They can be successfully overwintered outdoors under a frost

blanket or in an unheated greenhouse.

Creeping Phlox (Bare Root)

• Since this is an evergreen perennial, it should be potted up

immediately upon receipt.

• Pot into wide, shallow containers such as a 7-8 inch mum pan or

azalea pot. Standard 1-gal containers are too small for bare root

creeping phlox.

• Excellent root to soil contact is essential! Take care when potting

up bare root creeping phlox to make sure all of the fine root

mass is covered.

• Water thoroughly after potting to allow the soil to settle around

the roots. Then water lightly until new growth appears.

• Creeping Phlox needs high light levels, good air circulation, cool

temperatures (40-50°F), and an EC rate of 1.5-2.5 using the pour

through method to thrive.

• For spring planting, pot plants up in late March or early April (in

the north) and place directly outside under white, lightweight,

breathable row cover. Monitor soil moisture daily and water through

the fabric as needed. Remove the row cover when buds appear.

Prepare to cover the plants again in the event of a late, hard frost.

26 | Walters Gardens


Culture Guide

Spigelia

This stunning perennial is native to the Eastern United States

and creates a splash of red in the landscape that will entice the

neighborhood hummingbirds to stop by for a snack. They are a very

versatile perennial, growing well in sun or part shade and in a wide

range of soils as long as drainage is good.

We are vegetatively propagating our spigelia to ensure good

uniformity, and will be offering it as grade 1 bare root divisions and as

72ct plugs. Bare root should be planted in spring to summer, and will

take 10-12 weeks to finish depending on temperature. 72cts should be

planted in late summer and overwintered for following spring sales.

Spigelia does require vernalization to bloom, provide at least 8

weeks between 35-40° F. Bare root material will have received the

needed cold treatment in the fields.

Higher light levels are preferable in production to produce higher

quality plants. If toning is needed, apply Uniconazole (Sumagic/

Concise) starting at 5 ppm.

Ferns

Good irrigation practices are essential when growing ferns. Plants

need to be kept moist, but not soaked, from the time they are potted

up until they are planted in the ground. It is best to water early in

the day to allow the fronds plenty of time to dry before nightfall.

Allow the soil to dry slightly between waterings.

Ferns can be sensitive to high salt levels incurred from fertilizing.

Aim for an EC rate of 1.0-1.5 using the pour through method and

use about half the amount of fertilizer you would use with other

perennials.

To prevent sun scorch in summer, grow ferns under at least 50%

shade in the north and up to 70% shade in the south.

Ferns should be planted before mid-August or wait until the

following spring to ensure survival. Potting them up early will give

them an adequate amount of time to become established before

overwintering. Upon receipt of your order, it is best to place them in

a cool, shaded location.

Ornamental Grasses and Sedges

• Roots must be kept moist prior to potting and plants must be

kept from freezing, preferably above 45°F, both before and after

transplanting.

• Pot up in a well-drained, commercial soil mix.

• Water sparingly until a significant amount of new growth appears.

• Most grasses are moderate feeders and perform well with an EC

rate of 2.0-3.0 (pour through method). Sedges are lighter feeders,

preferring an EC rate of 1.5-2.0 (pour through method).

Cool Season Grasses

Cool season grasses are at their prime during the cooler months

of fall, winter, and spring, and usually bloom before the warmer

summer weather arrives. Many are evergreen. Cool season

grasses should be received in fall or early spring and be potted

up immediately. They will put on the most growth during these

cooler months. Though they should be kept from freezing over the

winter, they do not require much, if any, supplemental heat. Cool

season grasses include: Calamagrostis acutiflora, Deschampsia,

Festuca, Helictotrichon, and Sesleria.

Warm Season Grasses

Warm season grasses grow most actively during the warmer

months, then flower in late summer or fall. Most go completely

dormant in winter. Warm season grasses are not recommended

for fall planting. It is best to receive them from early spring

through late summer and pot them up immediately. If necessary,

provide supplemental heat to keep the plants at 60°F or higher to

stimulate top growth. Warm season grasses include: Andropogon,

Bouteloua, Calamagrostis brachytricha, Hakonechloa, Miscanthus,

Panicum, Pennisetum, Schizachyrium, and Sporobolus.

Sedge

Though it is not a true grass, Sedge, or Carex, tends to grow much

like a warm season grass. It is best to receive Carex from early

spring through late summer rather than in the fall.

Ornamental & Edible Strawberries from Plugs

• Plant ornamental and edible strawberries such as Fragaria a.

‘Tristan’ in spring for summer sales.

• Plant one 72ct plug per 1-Qt or trade 1-Gal container.

• Grow these plants cool at 55-60°F with high light intensities for

best results. Temperature may be raised slightly once plants are

rooted out. Plants will generally finish in 1-Qt containers in 4-6

weeks and in trade 1-Gal containers in 8-10 weeks.

• Use a well-drained, balanced soil with a pH of 5.8-6.5 and an EC

rate of 1.5-2.5 using the pour through method.

• Maintain slightly moist soil consistently. Do not let plants dry out.

Edible Strawberries from Bare Root

• Plant edible strawberries such as ‘Allstar’ in spring for summer

sales.

• Plant one bare root per 1-Qt or trade 1-Gal container.

• Take care when potting to spread the roots well in the container

and to keep the crown at the soil line. Do not pot these deep.

• Water roots in well after potting to eliminate air pockets.

• Follow remaining guidelines for Ornamental & Edible Strawberries

listed above.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 27


Culture Guide

Tropicals

• Recommended pot size depends on the variety. Colocasias

typically require larger containers; plants will grow larger if given

more root space. Smaller tropicals can be finished in 4-in to 1-gal

containers.

• Tropicals can be grown successfully in a general perennial soil mix.

• Grow warm with a constant temperature in the upper 60s,

and provide high light intensities as this will mimic their native

environment.

• Maintain average to high moisture levels. Do not let these plants

dry out.

• Once plants are actively growing, feed with 20-10-20 water

soluble fertilizer at a rate of 75-125ppm Nitrogen at every

watering.

• Not all tropicals grow at the same rate. For example, Colocasias

are very fast growers compared to Cordylines. Plan your timing

accordingly.

• Some tropical temperennials have very tender foliage that is

easily torn or damaged. Take care when handling them.

DIGIPLEXIS®

DIGIPLEXIS® are a combination of hardy Digitalis purpurea and the

Canary Islands native Isoplexis canariensis. These award-winning

plants have the enviable traits of long season of flowering, heavy

flower performance, and vigorous growth rates.

DIGIPLEXIS® are vigorous growers and a 2-Gallon container is

recommended.

Plants finish in 8-10 weeks at 55-60°F. This is a tender perennial—if

temperatures fall below 38°F there is a good chance of damaging

the plant.

High light levels and cool temperatures will keep them neatly

compact. Flower color will be significantly more vibrant when grown

in direct sunlight than under clear plastic.

Moderate to consistent moisture levels are recommended. Drip

irrigation is very effective at getting water past the thick foliage to

the roots. Irrigating in the morning is more effective as this plant

does not like to sit too wet for too long.

DIGIPLEXIS® are moderate feeders. A constant liquid feed of 100-

125ppm Nitrogen during the rooting stage and increased to 200-

250ppm Nitrogen just before blooming is recommended.

The suggested EC rate is 2.0-3.0 using the pour through method.

Pinching the main flower stem will stimulate production of additional

stems and bulk up the plant. If left unpinched the main flower stem

will grow very tall and require staking.

Succulents (Non-Hardy)

• Finish in 1-qt containers using a coarse, very well-drained soil.

• Be sure to wear heavy gloves when transplanting to avoid injury

as some Agave and Mangave varieties have sharp spines.

• Grow warm with a constant temperature in the upper 60s,

and provide high light intensities as this will mimic their native

environment.

• Succulents grow best at a moderate moisture level except for

the slow growing Agave which prefer low to average moisture.

Hold Agave dry but give them an occasional deep watering.

• Succulents grow well with average fertility.

• Succulents tend to be slow growers so plan your timing

accordingly.

Mangave

Mangave are a hybrid created by crossing Manfreda and Agave,

and the result are fun plants that have the best traits of both of their

parents. Mangave have the great habit of Agave, but are quicker

to produce and display interesting patterns due to the manfreda

parentage.

Walters Gardens offers Mangave in 72ct plugs, both as single variety

trays and in two pre-mixed trays. Plugs should be planted in quarts

in early summer, and will take between 8-15 weeks to finish a quart

depending on variety. Plants with broad foliage tend to be quicker

to finish than narrow foliaged varieties.

Mangave love warm temperatures, and should be grown under

68-75°F + conditions. They can be held at cooler temperatures

down to 60°F once the desired size is achieved.

The distinctive colors and

spotted patterns of mangave are

intensified by UV light. During

the winter months or when

grown in a greenhouse under

poly, the coloration and spotting

will be subdued.

A common misconception about

mangave is that they should be

grown dry. They actually require

moderate moisture in order to

achieve the best growth, but

avoid saturated conditions as

that can lead to crown and root

rots – a good rule of thumb is to

water mangave like you would a

hosta.

While a tray may arrive “green”,

a few weeks under UV or sunlight

will bring out the bright colors

28 | Walters Gardens


Grower’s Reference Chart

Recommended EC Using

the Pour Through Method

Consistent Water Needs

Grow Cool: 50-60° F

Grow Warm: 65-70° F

Start Warm: 65-70° F

Evergreen in Some or

All Climates

Average Water Needs

Long Days to Break

Dormancy

Recommended pH

Low Water Needs

Easy to Grow

Full Shade

Part Shade

Full Sun

Hardy Perennials

Achillea 5.5-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Aconitum 5.8-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Agapanthus 6.2-6.5 1.5-2.5 ✺ ✺ ✺ ✺

Agastache 5.8-6.2 1.2-1.4 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Ajuga 6.0-6.5 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺ ✺

Alcea 5.5-6.2 2.0-3.0 ✺ ✺ ✺

Alchemilla 5.8-6.5 1.0-1.2 ✺ ✺ ✺ ✺ ✺ ✺

Allium 5.8-6.8 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Amsonia 5.6-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Anemone 5.8-6.4 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Anthemis 5.5-6.2 1.5-2.0 ✺ ✺ ✺ ✺

Aquilegia 5.8-6.4 1.0-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Arabis 5.5-6.5 1.0-1.5 ✺ ✺ ✺ ✺ ✺

Aralia 5.0-7.4 2.0-3.0 ✺ ✺ ✺ ✺

Armeria 5.8-6.2 1.2-1.4 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Artemisia 5.5-6.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Aruncus 5.5-6.5 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Asarum 5.8-6.2 1.0-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Asclepias tuberosa 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Aster 6.0-6.5 2.0-3.0 ✺ ✺ ✺ ✺ ✺

*For more information visit the Culture Sheets section of our website.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 29


Grower’s Reference Chart

Recommended EC Using

the Pour Through Method

Consistent Water Needs

Grow Warm: 65-70° F

Start Warm: 65-70° F

Average Water Needs

Evergreen in Some or

All Climates

Grow Cool: 50-60° F

Long Days to Break

Dormancy

Recommended pH

Low Water Needs

Easy to Grow

Full Shade

Part Shade

Full Sun

Astilbe 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Baptisia 5.8-6.5 2.0-3.0 ✺ ✺ ✺ ✺

Belamcanda 5.8-6.5 2.0-3.0 ✺ ✺ ✺ ✺

Bergenia 5.8-6.5 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Brunnera 5.8-6.2 2.0-2.5 ✺ ✺ ✺ ✺ ✺

Buddleia 5.8-6.5 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Calamintha 6.0-6.6 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Campanula 5.8-6.2 1.0-1.2 ✺ ✺ ✺ ✺

Cerastium 6.0-6.5 1.2-1.5 ✺ ✺

Ceratostigma 5.8-6.2 1.5-2.5 ✺ ✺ ✺ ✺ ✺

Cimicifuga 5.8-6.8 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Clematis (Bush) 5.8-6.2 2.0-3.0 ✺ ✺ ✺

Convallaria 5.8-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Coreopsis 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Corydalis 5.8-6.8 1.0-1.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Crocosmia 5.8-6.8 1.5-2.0 ✺ ✺ ✺

Delosperma 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Delphinium 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺

Dianthus 5.5-5.8 1.25-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Dicentra 5.5-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Digitalis 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Echinacea 5.5-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Echinops 5.8-6.8 1.0-1.5 ✺ ✺ ✺ ✺ ✺

Epimedium 5.8-6.2 1.0-1.75 ✺ ✺ ✺ ✺ ✺ ✺

Eryngium 5.5-6.5


Grower’s Reference Chart

Recommended EC Using

the Pour Through Method

Consistent Water Needs

Grow Warm: 65-70° F

Start Warm: 65-70° F

Average Water Needs

Evergreen in Some or

All Climates

Grow Cool: 50-60° F

Long Days to Break

Dormancy

Recommended pH

Low Water Needs

Easy to Grow

Full Shade

Part Shade

Full Sun

Geum 5.8-6.4 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Gypsophila 5.8-6.2 1.25-2.0 ✺ ✺ ✺ ✺ ✺

Heliopsis 5.8-6.2 2.5-3.0 ✺ ✺ ✺ ✺ ✺

Helleborus 5.8-6.4 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Hemerocallis 6.0-6.5 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Heuchera 5.5-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Heucherella 5.5-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺ ✺

Hibiscus 5.5-6.2 2.5-3.5 ✺ ✺ ✺ ✺ ✺ ✺

Hosta 5.8-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Iberis 5.5-6.2 1.2-1.4 ✺ ✺ ✺ ✺

Iris (Japanese) 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Iris (Lousiana) 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Iris (Siberian) 5.0-6.8 1.0-1.5 ✺ ✺ ✺ ✺ ✺

Knautia 5.8-6.5 1.5-2.0 ✺ ✺ ✺ ✺

Kniphofia 5.5-6.0 1.5-2.0 ✺ ✺ ✺

Lagerstroemia 5.5-6.0 2.0-3.0 ✺ ✺ ✺ ✺ ✺ ✺

Lavandula 5.8-6.2 1.25-1.75 ✺ ✺ ✺ ✺

Leucanthemum 5.8-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Liatris 6.5-7.0 1.5-2.0 ✺ ✺

Ligularia 5.8-6.2 1.5-2.5 ✺ ✺

Liriope 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺ ✺

Lobelia 5.8-6.4 1.1-1.3 ✺ ✺ ✺ ✺

Lupinus 5.8-6.2 2.0-2.5 ✺ ✺ ✺ ✺ ✺

Lychnis 5.8-6.8 1.0-1.5 ✺ ✺ ✺ ✺

Malva 5.2-6.5 2.0-2.5 ✺ ✺ ✺

Monarda 5.8-6.4 1.5-2.5 ✺ ✺ ✺ ✺ ✺

Mukdenia 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺

Nepeta 6.0-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Oenothera 5.8-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Ophiopogon 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Paeonia (Garden) 6.5-7.0 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Paeonia (Intersectional) 6.5-7.0 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Papaver 5.5-6.2 1.5-2.5 ✺ ✺ ✺

*For more information visit the Culture Sheets section of our website.

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Grower’s Reference Chart

Recommended EC Using

the Pour Through Method

Consistent Water Needs

Grow Warm: 65-70° F

Start Warm: 65-70° F

Average Water Needs

Evergreen in Some or

All Climates

Grow Cool: 50-60° F

Long Days to Break

Dormancy

Recommended pH

Low Water Needs

Easy to Grow

Full Shade

Part Shade

Full Sun

Penstemon 5.9-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Perovskia 6.0-6.5 1.2-1.4 ✺ ✺ ✺ ✺ ✺

Phlox paniculata 5.8-6.5 2.0-3.5 ✺ ✺ ✺ ✺

Phlox subulata 5.8-6.2 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Platycodon 5.5-6.0 1.5-2.0 ✺ ✺ ✺ ✺

Polygonatum 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Primula 5.8-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Pulmonaria 5.6-6.8 2.0-2.5 ✺ ✺ ✺ ✺ ✺

Rudbeckia 5.8-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Salvia 5.8-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Sanguisorba 5.5-7.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Saponaria 6.8-7.5 1.0-1.5 ✺ ✺ ✺

Scabiosa 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Sedum 5.8-6.5 2.0-3.5 ✺ ✺ ✺ ✺

Sempervivum 5.8-6.2 1.0-1.5 ✺ ✺ ✺ ✺

Sisyrinchium 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Spigelia 5-5=6.5 2.0-3.0 ✺ ✺ ✺ ✺ ✺ ✺

Stachys 5.8-6.5 1.0-1.5 ✺ ✺ ✺ ✺ ✺ ✺

Stokesia 5.8-6.8 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Tanacetum 5.8-6.8 1.5-2.0 ✺ ✺ ✺

Thymus 6.0-7.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Tiarella 5.5-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Tradescantia 6.0-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Tricyrtis 5.8-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Trollius 5.8-6.8 1.5-2.0 ✺ ✺ ✺ ✺

Vernonia 5.5-7.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Veronica 5.5-6.2 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Viola 5.8-6.8 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Yucca 6.0-6.5 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Ferns

Athyrium 5.5-6.5 1.0-1.5 ✺ ✺ ✺ ✺ ✺

Dryopteris 5.5-6.5 1.0-1.5 ✺ ✺ ✺ ✺ ✺ ✺

Matteuccia 5.5-6.5 1.0-1.5 ✺ ✺ ✺ ✺ ✺

*For more information visit the Culture Sheets section of our website.

32 | Walters Gardens


Grower’s Reference Chart

Recommended EC Using

the Pour Through Method

Consistent Water Needs

Grow Warm: 65-70° F

Start Warm: 65-70° F

Average Water Needs

Evergreen in Some or

All Climates

Grow Cool: 50-60° F

Long Days to Break

Dormancy

Recommended pH

Low Water Needs

Easy to Grow

Part Shade

Full Shade

Full Sun

Grasses & Sedges

Andropogon 5.8-6.3 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Bouteloua 5.5-7.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Calamagrostis 5.8-6.3 2.0-3.0 ✺ ✺ ✺ ✺ ✺

Carex 5.8-6.3 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺ ✺

Festuca 5.8-6.3 1.5-2.0 ✺ ✺ ✺ ✺ ✺ ✺

Hakonechloa 5.8-6.3 1.75-2.25 ✺ ✺ ✺ ✺ ✺ ✺

Helictotrichon 5.8-6.3 1.5-2.0 ✺ ✺ ✺ ✺

Imperata 5.8-6.3 2.0-2.5 ✺ ✺ ✺ ✺

Miscanthus 5.8-6.3 2.0-3.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Panicum 5.8-6.3 2.5-3.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Pennisetum 5.8-6.3 2.0-3.5 ✺ ✺ ✺ ✺ ✺ ✺

Schizachyrium 5.8-6.3 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Sesleria 5.5-7.0 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Sporobolus 5.8-6.3 1.5-2.5 ✺ ✺ ✺ ✺

Fruits & Vegetables

Asparagus 5.5-6.2 1.5-2.0 ✺ ✺ ✺ ✺ ✺

Rhubarb 6.0-6.5 1.5-2.0 ✺ ✺ ✺ ✺

Strawberries 5.8-6.5 1.5-2.5 ✺ ✺ ✺

Tropicals

Colocasia 6.0-6.5 2.0-2.5 ✺ ✺ ✺ ✺ ✺ ✺ ✺ ✺

Cordyline 5-5-6.5 1.5-2.5 ✺ ✺ ✺ ✺ ✺ ✺

Digiplexis® 5.5-6.0 2.0-3.0 ✺ ✺ ✺

Succulents (Non-Hardy)

Agave 6.0-6.5 0.5-1.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Hansara 6.2-6.8 0.5-1.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Manfreda 6.0-6.5 0.5-1.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

Mangave 6.0-6.5 0.5-1.0 ✺ ✺ ✺ ✺ ✺ ✺ ✺

*For more information visit the Culture Sheets section of our website.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 33


Plant Health

Walters Gardens has made a strong commitment to provide only the

most healthy, vigorous product to our customers. All of our crops are

tested regularly for the most common viruses as well as additional

genus-specific viruses where needed. Our fields and greenhouses are

also regularly scouted for signs of pests or diseases. In addition to the

dedicated efforts of our Growers and Plant Health Team, we make an

effort company-wide to maintain clean and preventative practices to

limit the spread and introduction of pests, diseases, and viruses.

How to Identify

Virus-Indexed Plants (VIP)

A virus-indexed variety is one that has been tested and deemed

free of the viruses listed (right) up to the point of testing. A bow

tie symbol is located in the key code of each variety that has

been virus-indexed.

Sustainable Production Practice

and Integrated Pest Management

In the Fields

Understanding the vital importance of plant health, we remain

vigilant in preventing problems in our fields. Before a crop is planted

in the field, we make sure our planting stock is clean and diseasefree.

We then diversify our plantings so that disease prone items are

never planted in the same place twice. All of the equipment used

to plant and harvest our hosta stock blocks is sanitized between

cultivars. We also scout weekly for weeds, insect damage, unusual

variations in growth, trueness to type, and overall plant health.

In the Greenhouse

Prevention is key when it comes to pest and disease management

in our greenhouses. We do weekly scouting for any pest, disease, or

nutritional issues and do preventative spraying in regular intervals

to prevent the onset of disease. Our goal is to catch problems at the

earliest stage possible and to target the treatment to the specific

crop before it spreads to other plants. When treatment is needed,

we use beneficial insects or reduced-risk pesticides which target

specific pests rather than using broad spectrum chemicals. We have

not used neonicotinoid containing products on our production crops

since 2014.

Virus Prevention and Index

We take great pride in the attentiveness of our Plant Health and

Greenhouse staff when it comes to identifying and preventing viruses

in our plants. All of our plants are tested on a regular basis regardless

of appearance or history. Because there is always risk of a crop being

exposed to a virus, and more so in a field environment, we will not

give VIP status to a variety if we feel there is too much risk of infection

between testing and shipping. If a variety is prone to viral infection,

extra steps are taken to ensure that our stock and production lines

always start with clean material.

Plants are tested here at Walters Gardens, Inc. for the viruses listed

below and are designated with a bow tie symbol.

General Perennials

• Alfalfa Mosaic Virus (AMV)

• Alternanthera/Papaya Mosaic Virus (AltMV/PapMV)

• Arabis Mosaic Virus (ArMV)

• Cucumber Mosaic Virus (CMV)

• Impatiens Necrotic Spot Virus (INSV)

• Potyvirus Group (POTY)

• Tobacco Mosaic Virus (TMV)

• Tobacco Ringspot Virus (TRSV)

• Tobacco Streak Virus (TSV)

• Tomato Aspermy Virus (TAV)

• Tomato Ringspot Virus (ToRSV)

• Tomato Spotted Wilt Virus (TSWV)

Dianthus

• 12 General Perennial tests

• Carnation Etched Ring Virus (CERV)

• Carnation Latent Virus (CLV)

• Carnation Mottle Virus (CarMV)

• Carnation Necrotic Fleck Virus (CNFV)

• Carnation Ringspot Virus (CRSV)

Hosta

• Arabis Mosaic Virus (ArMV)

• Cucumber Mosaic Virus (CMV)

• Hosta Virus X (HVX)

• Impatiens Necrotic Spot Virus (INSV)

• Tobacco Ringspot Virus (TRSV)

• Tobacco Streak Virus (TSV)

• Tomato Ringspot Virus (ToRSV)

• Tomato Spotted Wilt Virus (TSWV)

Anemone, Astilbe, Dicentra, Epimedium, Iris, Paeonia

• 12 General Perennial tests

• Tobacco Rattle Virus (TRV)

34 | Walters Gardens


Common Insects Affecting Herbaceous Perennials

Plant Health

Pest

Biological Control

Biological Control Compatible

Insecticides

Other Insecticides

Aphid

Aphidoletes aphidimyza, Aphidius

colemani, Chrysopa carnea,

Adalia bipunctata

Azatin O, Botanigard, Endeavor,

Rycar

Altus, Horticultural oil, Orthene

Black Vine Weevil

Steinernema spp. and

Heterorhabditis spp.

Botanigard

Orthene drench for larvae;

Orthene or Talstar for adults

Caterpillars

Chrysopa carnea

Azatin O, Botanigard, DiPel,

Overture

Conserve, Decathlon,

Mainspring, Orthene

Fungus Gnats & Shorefly Larvae

Steinernema feltiae, Hypoaspis

miles, Atheta coriaria

Adept, Citation, Distance, Gnatrol

Duraguard (SF), Talstar (FG)

Leafhoppers Chrysopa carnea Rycar Altus, Orthene

Leafminers Steinernema spp, Diglyphus isea Azatin O, Conserve, Citation Avid, Conserve, Orthene

Mealybugs

Chrysopa carnea,

Cryptolaemus spp.

Rycar

Altus, Orthene Drench

Mites

Phytoseiulus persimillis,

Amblyseius californicus

Floramite, Hexygon, Ovation,

Shuttle O, Sultan

Avid, Judo, Pylon, Sanmite,

Tetrasan

Scale

Amblyseius spp, Chrysopa

Carnea, Cryptolaemus spp.

N/A

Altus, Horticultural oil, Suffoil-X,

Orthene Drench

Slugs & Snails N/A Sluggo Mesurol

Thrips

Amblyseius cucumeris,

Amblyseius swirskii, Orius

insidiosus, Steinernema feltiae

Botanigard, Mainspring, Overture

Altus, Avid, Conserve, Mesurol,

SuffOil-X

Whitefly

Amblyseius swirskii, Encarsia

formosa, Eretmocerus eremicus,

Delphastus spp.

Azatin O, Botanigard, Distance,

Endeavor, Rycar

Altus, Avid, Decathlon, Judo,

Sanmite, SuffOil-X

Note: Refer to product label for specific application instructions.

Aphid Slug Leafminer damage

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 35


Plant Health

Common Diseases Affecting Herbaceous Perennials

Disease

Alternaria Leaf Spot

Anthracnose Leaf Spot

Aster Yellows

Bacteria Leaf Spots (ex:

Xanthamonas, Pseudomonas)

Botrytis

Cercospora Leaf Spot

Downy Mildew

Fusarium Crown or Root Rot

Galls-Agrobacterium

tumefaciens (Crown Gall) &

Rhodococcus fascians (Leafy

Gall)

Favorable Environmental

Conditions for Development

Warm temps, humidity,

prolonged standing water on

leaf surface

Warm temps, prolonged

standing water on leaf surface

Symptoms of infection usually

most evident mid-spring thru

summer

Warm temps, prolonged

standing water on leaf surface

and high humidity

Moderate to cool temps, high

humidity or prolonged standing

water on leaf surface

Moderate to cool temps and

prolonged leaf wetness

Warm to cool temperatures,

prolonged standing water

on leaf surface, high relative

humidity, cloudy days

Warm soil, excess water and/

or fertilizer

Symptoms of infection usually

most evident mid to end of

summer

Typical Symptoms Cultural Management Chemical Management

Reddish or purple spots usually

with brown/necrotic centers

Tan, black, or brown leaf spots

irregular spots; sometimes

spores can be observed in spot

with hand lens

Flowers become green and

distorted; new shoots are

yellow, spindly, & stunted.

Red, brown, black, purple

irregular or round shaped spots

with yellow halo

White/grey spores; primarily

attacks dead, decaying, or

diseased plant parts and

spreads to healthy plant tissue

if uncontrolled.

Spots with tan centers and

purple borders; sometimes small

black spores visible in center

Faint or bright red/purple/tan

angular leaf spots (similar to foliar

nematodes); white fuzzy spores

may be seen on leaf undersides

Initially older leaves yellow & wilt;

in time, roots & crown become

completely brown with rot

Crown Gall-Tumors in the shape

of irregular spheres. Leafy Gall-

Excessive shoot proliferation

without elongation.

Good air flow around plants,

Keep foliage dry, remove

diseased foliage

Good air flow around plants, Keep

foliage dry, remove diseased

foliage

Clean stock

Clean stock

Good air flow around plants to

dry out decaying plant tissue

Good air flow around plants,

Keep foliage dry, remove

diseased foliage

Good air flow around plants; Keep

foliage dry, decrease relative

humidity if it's too high, remove

diseased foliage

Avoid overwatering, reduce

fertilization

Clean stock

Affirm WDG, Broadform, Chipco

26019, Daconil Ultrex, Heritage,

Medallion, Pageant

Daconil Ultrex, Heritage,

Broadform, Pageant, Medallion,

Cease

Monitor for 6-spotted Aster

leafhopper (the Aster Yellows

vector) and start control early

in spring.

Camelot, Kocide, or Phyton 27

can reduce symptoms/spread,

but will not eliminate bacteria

Affirm, Broadform, Chipco

26GT, Daconil Ultrex, Decree,

Medallion, Milstop/Cease,

Pageant, Terraguard

Daconil Ultrex, Eagle, Heritage,

Protect

Adorn, Fenstop, Micora, Orvego,

Segovis, Segway, Stature,

Subdue

Chipco 26GT, Heritage,

Medallion, Pageant, Terraguard

None

Note: Refer to product label for specific application instructions.

Aster Yellows damage on Echinacea Crown Gall Downy Mildew

Hosta with Anthracnose

36 | Walters Gardens


Plant Health

Common Diseases Affecting Herbaceous Perennials

Disease

Phytophthora Root/Crown Rot

Powdery Mildew

Pythium Root/Crown Rot

Rhizoctonia Crown Rot

Rhizoctonia Web Blight (Foliar

Blight)

Rust

Septoria Leaf Spot

Thielaviopsis Root/Crown Rot

Virus

Favorable Environmental

Conditions for Development

Excess soil moisture or root tips

in standing water under pots,

excess fertilizer, plant stress

Moderate or cool temps, high

humidity, cloudy days

Excess soil moisture or root tips

in standing water under pots,

excess fertilizer, plant stress

Warm temps, high humidity,

excess water and/or fertilizer,

plant stress

Warm temps, prolonged

standing water on leaf surface,

dense canopy

Moderate temps, prolonged

standing water on leaf surface

& high humidity

Moderate temps, prolonged

standing water on leaf surface

& high humidity

Excess soil moisture, high soil

pH (>6.0), cool soil temps, plant

stress

Symptoms usually most evident

mid-spring thru early summer, can

persist or disappear during summer

Typical Symptoms Cultural Management Chemical Management

Yellow, stunted or wilted plants,

roots turn brown, sometimes

outer root tissue pulls away,

leaving only vascular tube

Powdery white/grey spots on

leaf surface that spread to cover

whole leaves.

Yellow, stunted or wilted plants,

roots turn brown, sometimes

outer root tissue pulls away,

leaving only vascular tube

Foliage may turn yellow and wilt;

reddish brown lesions/cankers on

infected roots and crown

Foliage becomes water-soaked and

rots, sometimes the brown web-like

growth if the fungus is noticeable

Sometimes brown, red, or

orange leaf spots on upper leaf;

round, raised brown or orange

pustules on the underside of leaf

Spots have red/purple margins

with tan, necrotic centers (can

look similar to Alternaria) or

brown necrotic angular spots

Lower leaves turn yellow & wilt;

roots start with dark brown or

black spots & eventually turn

completely black with rot

Ringspots, mosaic, mottling,

stunted growth, necrotic or

chlorotic spots, leaf distortion

Avoid overwatering, reduce

fertilization, avoid plant stress

Good air flow; remove diseased

foliage

Avoid overwatering, reduce

fertilization, avoid plant stress

Avoid overwatering, reduce

fertilization

Good air flow around plants,

Keep foliage dry, remove

diseased foliage

Good air flow around plants;

Keep foliage dry, remove

disease foliage

Good air flow around plants,

Keep foliage dry, remove

diseased foliage

Keep soil pH≤6.0, warm soil

temps (>65 degrees); avoid

overwatering, do not reuse pots

or soil

Clean stock

Adorn, Micora, Segovis, Subdue,

Truban

Broadform, Eagle, Heritage,

Milstop, Pageant, Pipron,

Terraguard

Segovis, Subdue, Truban

Affirm, Broadform, Chipco

26GT, Cleary 3336, Heritage,

Medallion, Pageant

Affirm, Broadform, Clearys

3336, Daconil Ultrex, Eagle,

Heritage, Pageant, Palladium.

Broadform, Clearys 3336,

Eagle, Heritage, Mural, Protect

DF, Pageant

Broadform, Clearys 3336,

Daconil Ultrex, Heritage,

Pageant

Affirm, Banrot, Clearys 3336,

Medallion, Terraguard

None

Note: Refer to product label for specific application instructions.

Virus in Phlox Phytophthora Root/Crown Rot

Powdery Mildew Rust

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 37


Summer / Early Fall Planting &

Overwintering Recommendations

Summer & Fall Planting

Many experienced growers know that late

summer and early fall are excellent times

for planting perennials. Trials have shown

that many varieties of perennials have a

tremendous advantage when started the

season prior over those planted in spring.

They are stronger, more well-established,

display mature characteristics, and have

a higher perceived value. The pictures on

the next page show a few key genera that

benefit greatly from late summer planting.

A trial conducted at Walters Gardens

comparing the finish rates of freshly dug,

actively growing hostas to those of freshly

dug, dormant hostas grown in summer

demonstrated that those finished from

dormant plants are far superior in size, bulk,

and root mass than those finished from

actively growing plants.

On p. 39 you’ll find a chart listing some

types of perennials that benefit greatly

from summer and early fall planting.

Perennials such as Hosta and Hibiscus

require long days and some heat to grow,

so they need to be planted in summer

rather than fall when the light intensities

are greater and temperatures are warmer.

Note on this chart the color coding which

indicates whether the plants should ideally

be overwintered indoors or out.

Planting Bare Root Hostas in Summer

As a result of the trial, bare root hostas

are now dug from our fields in early

spring before they break dormancy and

held in freezers until they are shipped to

our customers from early June into early

August. We recommend that our customers

receive their bare root hostas as early in

summer as possible to take advantage of

the long, warm growing days, resulting in a

higher quality finished crop.

Overwintering

Precaution

If properly cared for going into

winter, perennials that are potted

up in summer and early fall should

overwinter well and emerge as large,

vigorous plants in spring. Overwintering

methods are described in the section

below. If you do not have the necessary

facilities for overwintering your

perennials, we suggest that you have

your order shipped in spring rather than

in summer or fall.

Factors such as soil moisture,

temperature fluctuations, and root

development in the container can

greatly affect a plant’s survival. Since

there are so many factors beyond our

control, Walters Gardens, Inc. does

not guarantee the survival of plants

overwintered in containers or in the

ground.

38 | Walters Gardens


Benefits of Summer and Early Fall Planting

You’ll save money.

When you grow perennials in summer and fall, there is no need for costly supplemental

heating or lighting. There’s less maintenance cost too since perennials

grown outdoors tend to grow more compactly because the wind, rain, and sun act

as natural PGRs.

You’ll save time and labor.

If you have overwintering capabilities, it is not necessary or even recommended to

plant all of your plants in spring. You’ll be better off if you time your crops properly,

splitting them into two groups: those best planted in summer or early fall (see chart

below for some examples) and those that are best planted in spring. This will save

time and make better use of your labor force–and of course lighten your stress

load–in the spring.

You’ll have larger, better performing

plants to sell in spring.

It’s no doubt that some perennials perform exponentially better if potted in summer

or early fall the year before they are sold. The perennials pictured here are great

examples of that.

Perennials build stronger root systems, have larger crowns that flush out nicer,

and are more floriferous the following spring when they are planted summer or fall

before. They’ll not only have a higher perceived value–they will deliver a stronger

performance for everyone from the grower to the consumer.

Overwintering Methods

If properly cared for going into winter, perennials that are potted up in summer and

early fall should overwinter well and emerge as large, vigorous plants in spring.

There are four basic methods of overwintering perennials: Thermoblanket Technique

• Sandwich Method • Minimally Heated Greenhouse or Polyhouse • Unheated Polyhouse

Under a Foam Blanket. Details on the following pages.

If you do not have the necessary facilities for overwintering your perennials, we

suggest that you have your order shipped in spring rather than summer or fall.

Left: Vernalized 20ct Hosta planted in a Premium 1-gal pot in spring.

Right: Fresh 20ct Hosta planted in a Premium 1-gal pot in late summer.

Hostas planted earlier develop more eyes, a better root system, and

more mature traits including proper variegation.

Left: Vernalized 20ct Monarda planted in a trade 1-gal pot in spring.

Right: Fresh 72ct Monarda planted in a Premium 1-gal pot in late

summer. The smaller plug filled out the larger container with fuller

foliage and more flowers, commanding a higher price at retail.

Summer Planting

Aruncus 72ct Grasses - Sedges Monarda 72ct

Brunnera 72ct Grasses - Warm season Perovskia 72ct

Coreopsis - Threadleaf 72ct Gypsophila 72ct Phlox - All

Daylilies - Any Size Heliopsis 72ct Rudbeckia ‘Little Goldstar’ 72ct

Dianthus 72ct Hostas Sedum - Upright forms 72ct

Dicentra 72ct Leucanthemum 72ct Stokesia 72ct

Euphorbia 72ct Ligularia 72ct Veronica 72ct

Geranium

Ligularia ‘Bottle Rocket’ benefits greatly from being planted the year

before it is sold. Those potted in late summer for sales the following

spring (right) are much fuller with larger leaves and more flowers per

plant than those potted up and sold the same spring (left).

Aquilegia 72ct

Epimedium 20ct

Grasses - Cool season

Paeonia - Garden and

Intersectional types

Early Fall Planting

Color Key:

Primula 72ct

Pulmonaria 72ct

Salvia 72ct

Tiarella 72ct

Best Overwintered Outdoors

Best Overwintered Indoors

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Overwintering Recommendations

Going into Winter

Rooting

The most important factor in overwintering perennials is having

healthy, well-rooted plants going into winter. Poorly rooted and potbound

plants tend to overwinter poorly. Time the delivery of your

bare root and plug perennials so that they can be well-rooted in

their containers by the time winter arrives.

Shearing and Moisture

• Evergreen Perennials

Perennials with evergreen foliage should not be cut back going

into winter. In order to prevent crushing or rotting the foliage,

they are best stored either on their sides or with an inverted tray

placed atop their foliage.

• Dormant Perennials

Most leafy perennials with dormant foliage will benefit from

being cut back and cleaned up before winter. Trim their foliage

back to the crown before storing them for winter.

• Moisture

When preparing your plants to be overwintered, check their roots

to make sure they are not dry. Most perennials like to have moist

roots going into winter since the moisture helps to insulate the

roots and prevent dessication. However, there are exceptions of

plants that prefer to be stored dry.

Baiting for Rodents

Several blends of rodent bait are available. Rotating the types

of baits used will increase their effectiveness. Begin baiting for

rodents about a month before covering your plants. This will help

to reduce their population going into winter. Place traps every

15-20 feet. Be sure to use pet-friendly traps to prevent accidentally

poisoning your pets.

Deciding When to Cover Your Plants

Timing is critical when it comes to covering your plants for winter.

If covered too early, heat can build up under the cover and damage

the plants. If the cover is left on too long in spring, the plants can

put on a soft flush of new growth that is easily damaged by late

frosts. When deciding when to cover your plants for winter, be sure

to monitor weather conditions closely. Nighttime temperatures near

freezing allow the plants to harden off before covering, but if the

forecast predicts nighttime temperatures below 25°F, it’s time to

cover your plants.

Dealing with Extremes

Extreme Cold

When perennials are overwintered above ground in containers,

they are effected to a greater degree by extreme winter

temperatures. Wide fluctuations between day and nighttime

temperatures, particularly in late winter and early spring, can

cause the plants to freeze and thaw, potentially damaging the

plants. Therefore, containerized perennials must be protected from

extreme cold when they are overwintered. They should be stored at

temperatures above freezing.

Excess Heat

On sunny days in late winter and early spring, heat can rapidly build

up in polyhouses. Good air circulation and ventilation is critical to

preventing plants from growing prematurely. Plants stored outside

on these sunny days may need to be uncovered and then recovered

based on the weather patterns.

A well-developed,

healthy root

system will solve a

number of common

overwintering issues

40 | Walters Gardens


Overwintering Recommendations

Overwintering Challenging Plants

Many kinds of perennials overwinter easily. However, some require

a little special treatment to make it through the winter in containers

successfully. Here are some tips for those types of plants.

Perennials that like to be kept dry

• Perennials that like to be kept dry during the winter should be

planted in a very well-drained growing media that can stay

relatively dry over the winter.

• Be sure to protect these types of plants from heavy fall rains

and from below freezing temperatures while they are being

stored for winter.

• Trim their foliage back and lay the pots on their sides if possible.

Make sure that no covering material comes in direct contact

with the foliage.

Ornamental Grasses

• Before potted grasses are stored for winter, water them

thoroughly. After they have gone dormant, they will need little

to no water until the temperatures begin to warm up again

the following spring. At that time, watering can be resumed as

needed to maintain proper moisture levels.

• After the plants have gone completely dormant for the winter,

you can trim the foliage all the way back. Do not cut the foliage

back until it is totally dormant.

• When overwintering grasses, make sure the temperature of the

root ball remains at or above freezing. Exposure to temperatures

below freezing may result in plant losses.

• Be sure to bait liberally for rodents since they have a fondness

for grasses.

Outdoor Overwintering Methods

Thermoblanket Technique

An insulated foam blanket (polyfoam or microfoam) is placed over the containers during the coldest months of the year. It is important

that the blanket be covered by white reflective nursery polyfilm, preferably 4-mil one year white poly. Pull the plastic tight over the

containers and secure the edges about 12 inches beyond the pots with concrete blocks.

Sandwich Method

Plastic sheeting or spun-bonded fabric is placed directly over the plants and then covered with a 12 inch deep layer of straw. The

straw layer is then covered with another layer of plastic sheeting. This technique is especially effective in northern regions where

temperatures remain consistently cold all winter long.

Frost Blanket Method (for hardy plants in zones 5 or warmer)

In this method, pots are set directly on the ground and covered with a heavy frost blanket once the temperatures dip below 25°F.

Pull the blanket tight over the containers and secure the edges about 12 inches beyond the pots with stakes or blocks. This method is

best used in northern climates where temperatures remain consistently cold all winter. Snow cover is beneficial, but not required for

overwintering success.

Indoor Overwintering Methods

Greenhouse or Polyhouse Kept at Low Temperatures

This overwintering method is the best for temperature control, especially if minimal heat is used. It also gives you more control over

moisture levels, growth, and heat build-up. Good air circulation and ventilation is critical with this method. Pubescent plants such as

Stachys are best overwintered in a polyhouse kept at low temperatures since these kinds of plants resent being covered with foam.

Unheated Polyhouse Under a Foam Blanket

With this method, the containers are stored in a narrow hoop house which is covered with white poly. Foam blankets are placed over the

plants. The house is not heated, so it is possible for plants to freeze using this method.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 41


Overwintering Methods

Echinacea

• Echinacea tends to overwinter better in larger containers, so we

recommend that you pot them up into 1-gal containers by early

fall at the latest. It is best to root them in completely before they

go naturally dormant.

• When receiving Echinacea in summer, we recommend that

you do one preventative fungicide drench immediately after

transplanting, and another drench about 14 days later. This

can help to protect the plants from disease as they begin to go

dormant in fall.

• Before overwintering, it is best to trim the plants back lightly

and allow what remains to go fully dormant, removing the dead

foliage in spring. Removing the foliage all the way to the crown

before overwintering encourages botrytis to set in, so take care

not to trim plants too far back (no more than halfway).

• When overwintering finished Echinaceas, hold plants at a

constant temperature of 38-40°F.

• Keep plants on the dry side, but not too dry or it may be difficult

to rehydrate them if they’ve dried out too much.

• Monitor salt levels and keep soluble salts low.

Hostas

Best Method - Overwintering in Unheated Structures Covered with

White Copolymer

• Place the pots inside the unheated structure and cover them

with microfoam. Turn larger pots on their sides if necessary.

• Bait liberally for mice.

• As the warmer days of spring arrive, remove the microfoam

cover.

• Once the volatile spring weather has subsided, take the white

copolymer off the structure and replace with 50% shade cloth (or

70% for blue hostas).

• If necessary, open the ends of the houses to provide ventilation.

Good Method - Overwintering in Minimally Heated Polyhouses

• Place the plants inside the minimally heated polyhouse and do

not cover them.

• Bait liberally for mice.

• Maintain temperatures above freezing. 35°F works well.

• Once the volatile spring weather has subsided and

temperatures have moderated, the plants may be moved

outside for finishing off.

• Be sure to provide at least 50% shade in the north and 80%

shade in the south.

Not Preferred - Overwintering in Cold Frames

• This overwintering method is not preferred because the plants

become exposed to extreme temperature changes along with

excessive wind and moisture once the covering is removed in

spring. This can cause foliage and root damage, possibly leading

to plant losses.

• If you must overwinter your hostas in a cold frame, turn the

larger pots on their sides if possible.

• Cover the pots with a layer of microfoam and a layer of white

copolymer. Remove this covering in early spring.

• Bait liberally for mice.

Peonies

It is best to overwinter potted peonies in a covered structure such as

a greenhouse or covered polyhouse.

Peonies require 500-700 hours at 32-37°F to be vernalized.

After that, it is best to let them acclimate naturally to outdoor

temperatures.

Please note: Peonies received after January 1 have already been

vernalized at Walters Gardens.

Tender Perennials

• Tender perennials should be treated as annuals and kept actively

growing in a warm area (minimum 55°F) through the winter

months.

• Succulents require very little water during the winter.

• Tropical Perennials prefer slightly moist soil.

42 | Walters Gardens


Additional Resources

Growing perennials is what we do, and we’ve been doing it for over 70 years. We are here to help our customers be more successful growers

so they can grow their businesses too. Our knowledgeable staff is always ready to help you find the answers to your questions, whether

you’re brand new to the industry or one of our many longtime loyal customers. In addition to the information provided in this Simple, Sensible,

Solutions® guide, here are some more recommended resources.

Recommended Websites

• Walters Gardens: www.WaltersGardens.com

• Proven Winners professional growers site: www.PWCertified.com

• Michigan State University Extension Floriculture Team —

Herbaceous Perennial Plant Production:

http://www.flor.hrt.msu.edu/perennials/

• Cornell University Cooperative Extension — 2012 Pest

Management Guide for the Production and Maintenance of

Herbaceous Perennials:

http://ipmguidelines.org/HerbaceousPerennials/

• University of Vermont Extension — Perry’s Perennial Pages:

http://www.uvm.edu/~pass/perry/

Recommended Books

Perennial Solutions—A Grower’s Guide to Perennial Production

Author: Paul Pilon

Respected Green Industry consultant

Paul Pilon has compiled a comprehensive

book covering all aspects of producing

perennial crops--propagation, fertility,

media, pest and disease management,

weed control, height control, and

overwintering. A large section of the

book is devoted to forcing perennials into

bloom to maximize sell through at the

retail level.

Visit www.PerennialSolutions.com for helpful articles and

additional information from Paul Pilon.

Ball Redbook—Volume 2: Crop Production 18th edition

Editor: Jim Nau

Offers professional tips on greenhouse

horticulture, from pest control to

plant nutrition. 162 flower, herb, and

vegetable crops are covered. An essential

resource for growers that offers advice

and techniques that work in real-life

production.

Trade Magazines

• GrowerTalks

• Green Profit

• Greenhouse Product News (GPN)

• Greenhouse Grower

• Garden Center Magazine

• Greenhouse Management

• Nursery Management

• Greenhouse Canada

Consults from Walters Gardens

We’re growers just like you and we’re here to help. If you need help

with something that is not covered here or have other growing

questions and concerns, please feel free to contact Walters

Gardens and we will do our best to help you resolve the issue. We

are happy to do whatever we can to help you be successful with

our bare root and plug perennials.

Pictured here are Laura Robles, Barb Balgoyen, and Janet DeVries.

Laura is our Trial Manager with many years of experience growing

finished product for trials, events, and retail. Barb and Janet both

have years of experience answering technical questions.

Laura Robles

Trial Manager

lsr@waltersgardens.com

Barb Balgoyen

Technical Customer Care Rep

1-800-925-8377 ext. 1202

blb@waltersgardens.com

Janet DeVries

Technical Customer Care Rep

1-800-925-8377 ext. 1206

jld@waltersgardens.com

Culture Sheets

Cultural sheets for most of the perennials we offer can be found

on www.WaltersGardens.com. They contain detailed information

such as growing temperatures, soil pH, planting level, weeks to

finish, watering, fertilizing, and pest and disease management

recommendations.

www.WaltersGardens.com • 1-888-925-8377 • sales@waltersgardens.com | 43


Walters Gardens

Home of Proven Winners® Perennials

P.O. Box 137 • Zeeland, MI 49464 • Phone: 888-925-8377 • Fax: 800-752-1879 • Email: sales@waltersgardens.com

www.WaltersGardens.com • www.PerennialResource.com • www.ProvenWinners.com

Copyright © 2019 Walters Gardens, Inc. No portion of this booklet may be reproduced without permission from Walters Gardens, Inc.

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