Transplanting Pink lady-slippers (Cypripedium acaule)

Images and text by William Cullina

No plant is more beloved and recognizable than the pink lady-slipper. Unlike most other

species of Cypripedium, it thrives in dry, acidic soils under a thin canopy of deciduous or

evergreen trees. It is found from Newfoundland to Saskatchewan south around the Great

Lakes to the southern Appalachians. In New England, it is by far the most common of

our five Cypripedium

species for the simple

reason that its

preferred habitat is so

abundant here. Still,

as development

converts forest to

subdivision, countless

thousands of pinklady-slippers

have

been bulldozed. It is a

species that is very

difficult to grow under

garden conditions, but

it is possible to

successfully transplant

it to an undisturbed

patch of forest that

offers similar growing

conditions. In a study

we conducted at the

New England Wild

Flower Society, of 75

plants rescued from a

condominium

development, 85

percent were still alive

and thriving after the

sixth season (when we

concluded the study).

Though pink ladyslippers

should never

be moved unless they

are in imminent

danger of destruction,

the purpose of this article is to show you how you can successfully rescue and reestablish

plants from property about to be developed.

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It is well known that all orchids have evolved a very sophisticated strategy for seed

germination. Orchid seeds are tiny and lack well developed embryos. To germinate, the

seed must come in contact with a

specific soil fungus which

surrounds the seed as if to digest it.

The fungal roots (hyphae)

penetrate the seed and then the

orchid turns the tide, digesting the

fungus instead. It seems that the

fungus gets nothing from this

arrangement except to be eaten, so

rather than the symbiotic

relationship found with most

mychorrizal interactions, in this

case the union is more properly

called micoparisitism. After 3-4

years in the soil growing larger at

the expense of the fungus, the seeding emerges and begins to photosynthesize for its

food. At this point, it is unclear how important the

fungus becomes to the more mature lady-slipper.

Mature plants can remain underground for several

years after a bad drought, predation, or other

trauma, so it does appear that some continued

relationship is important to the health of the plant.

One plant that I moved in 1990 grew for a few

years then disappeared, only to appear and bloom

again in 2005 then disappear in 2006 and reappear

in 2007 as a two-leaved but non-flowering plant!

Just how widespread the proper group of fungi is

through the range of the orchid is unclear, but

absence of plants in apparently suitable habitat

does not necessarily mean there is no fungus

present. The most important consideration when

choosing a spot for relocation is the pH of the soil,

the available light, and potential competition from

other plants. The pH of the soil is important

because unless the soil is extremely acidic, C. acaule is prone to attack by root diseases

that are naturally suppressed at low pH. Soils with a pH below 5.0 are optimal. You can

test the soil with inexpensive pH test kits or look for indicator plants that like a similar

habitat (obviously, if pink lady-slippers grow there already, it is ideal). In our area of

southern New England as well as most parts of Central and Northern New England, the

soils are considered to be very acidic. Pines, oaks, hickories, spruce, fir, and paper birch

are common canopy species in pink lady-slipper habitat. Some indicator plants to for at

ground level include:

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Dendrolycopodium dendroideum Chimaphila maculata Gautheria procumbens

(and other clubmosses) (spotted wintergreen) (wintergreen, checkerberry)

Vaccinium angustifolium Gaylussacia baccata Kalmia angustifolia

(lowbush blueberry and (black huckleberry) (sheep laurel)

other blueberries)

Pink lady-slippers do poorly in deep shade, and this is the most common reason they

disappear over time from a given woods. They are most abundant in either very old

forests with a mixed and broken canopy or in young forest regenerating after logging or

fire. Road cuts and other edge habitats are also good places to find them. I look for

places where the tree canopy has some gaps from windfalls or timber harvest to site

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plants rather than in total shade under a continuous canopy.

This is especially important under evergreens. Look for places where the sun breaks

through for an hour or so each day.

Chose areas where the ground is reasonably free of competition. Here huckleberries,

wintergreen, mountain laurel (Kalmia latifolia) and a small white pine indicate good

habitat. I will site the plant just in front of the dead branch in the center.

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Though in an emergency, you can successfully move pink lady-slippers at any time

during the growing season, I have had the best results when I moved them in late summer

just as the leaves begin to yellow. This plant flowered earlier in the season, but deer

nipped of the bloom stalk. C. acaule’s roots are very shallow and spread out from the

crown 8-24 inches in all directions, so care must be taken to damage them as little as

possible.

I use a pitchfork to lift the roots gently, coming in

at a shallow angle about 12 inches from the crown

and rocking the fork until the crown lifts up. At

this point I use my hands to help tease the roots free from tree roots and debris. Here the

plant has been lifted with little breakage of the roots and with some humus still

surrounding them.

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You can also

remove plants

bare-root as

long as you have

damp burlap to

cover them with

until them are

replanted. This

smaller

individual

has

one welldeveloped

bud

visible in the

center of the

image and a

moderately

sized root

system.

Blackened roots

are stained by humic acids in the soil but still healthy. The white roots are younger.

Lady-slipper

roots will

continue to live

and grow longer

over the course

of about 5 years.

However, if the

growing tip is

damaged on a

particular root, it

cannot grow

another. In this

image, the

healthy white

root began

growing this

spring (after

flowering) as

did the slightly

more stained

one at the left. Notice that this second root has lost its tip and can grow no

longer.

The

roots are all important to lady-slippers as they not only take up water and nutrients

(and perhaps carbohydrates from the fungus) but they also act as the primary foodstorage

organ for the plant during dormancy. If roots are cut or damaged during

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transplant, they will stop growing and be vulnerable to infection. The loss of more than a

few can spell disaster for the plant, as it has lost a good share of its food reserves and will

likely wither away over the next year or two. This is a common occurrence in gardens,

where a rescued or wild-collected plant will come up the first year, come back smaller the

next, and fail to return the third. C. acaule’s roots inhabit what is called the F horizon in

the soil. This

is the zone or

layer just

underneath the

unrotted leaves

and other

debris in this

image. A few

roots may pass

through the

narrow H

horizon and

into the black

and gray A

horizon. The

H horizon is

not topsoil, but

rather a porous

blend of

partially

decomposed

organic

materials.

When

replanting the

orchid, it is

essential that

you relocate

the roots in

this layer as

they will

often

rot if buried in

the heavier

horizons

beneath.

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I use a digging spade to scrape away the H horizon,

exposing but no removing the lighter A horizon beneath.

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Set the plant into this shallow hole and use your fingers to pack the duffy humus

(H horizon) you just scraped off

around the root mass (if the plant is

bare-root, be extra careful to work the

material in, around and between the

roots so as they are spread out).

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In this image, a bare-root plant has been set at the proper depth and is ready to be

repacked with duff.

Set the plant so that the tip of the white, pointed bud evident in this image lies just below

the surface when you are finished.

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The finished plant with

unrotted leaves spread

back over the roots once

they have been backfilled

with duff. By choosing a

suitable spot, disturbing

the soil horizons as little

as possible and locating

the roots at the proper

depth, I have maximized

this plant’s chances for

success. Other than a

good watering or two to

settle the soil, no

additional water or

supplements are needed.

The same plant the following spring with healthy leaves but no flowers. They are stiff

and just pale enough to let me know they are receiving enough light.

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Again, the same plant in its second spring, now with two growths and a beautiful bloom –

both signs that it is settled in and thriving! Notice how the wintergreen in the first picture

has spread beyond the dead branch and around the plant as it heads toward the light.

Good Luck!

©

2007 William Cullina