VERMICOMPOST: WORMS DO IT - Fairfax County Master Gardeners

VERMICOMPOST: WORMS DO IT
By Gretchen Stark, Master Gardener
Worm tunnels aerate the earth, and worms feed on decaying organic
matter, releasing worm manure, also called castings which are rich in
nutrients for plants. In fact, Charles Darwin believed that no other living
thing “has had such a profound impact on history as has the earthworm. ” 1
Gardeners have long recognized the importance of worms to plant health
and have sought ways to manage and increase the benefits worms
provide. Managed worm composting, or vermiculture is the long
established method for cultivating and harvesting the worm castings.
Laurie Short, horticulturist at Meadowlark Botanical Gardens in Vienna,
Virginia, is an enthusiastic advocate of worm composting. I interviewed her
about the vermiculture program at Meadowlark which has been in
operation since 2010. She finds it to be a low cost convenient way to
recycle kitchen scraps into a nutritious, organic soil additive.
The right worm
There are thousands of worm species, but it is the Eisenia Fetida (also
known as red worm, red wiggler, or compost worm) that has become the
champion of home worm compost bins. In the right conditions the Eisenia
Fetida multiplies rapidly, and each worm consumes half its body weight in
decaying kitchen scraps daily.
I have had worm composting in my basement since 2009 and have
watched with fascination as kitchen scraps have been transformed with
biological alchemy into three products:
Castings. The partially decayed organic material consumed by the worms
passes through a crop and gizzard, a strong muscle filled with grit, where it
is further ground up making it easy for intestinal bacteria, fungus and other
micro organisms to finish the decomposition process. When the worm
eventually expels it, it is called a cast. The castings have calcium, potash,
phosphate,and nitrogen in addition to antibacterial and insecticidal qualities
that can be easily absorbed by plant roots.
1 Christopher Lloyd, What on Earth Evolved? 100 Species that Changed the World (New
York:Bloomsbury,2009),p.97

Vermicompost or worm compost. refers to the materials in the worm
bin that include other, undigested, mostly decayed organic material and
microscopic organisms. It is rich in bacteria, and enzymes and has all the
benefits of the castings, too.
Vermicast refers to organic material converted totally to worm castings.
Since the worms have the habit of eating and re-eating all the materials in
the bin, worm castings confined in a bin with worms too long will be
recycled too many times and have fewer nutrients.
Benefits of worm composting
At Meadowlark the staff report that as a consequence of the vermiculture
program, no restricted or chemical pesticides or fungicides have been
needed in the greenhouse this year, although occasionally the
horticulturists use organic pesticides and fungicides. The plants are
healthier in the greenhouse and continue to be healthy as they are planted
in the outside garden areas. The pH range for the vermicompost varies
according to the acidity of the organic matter used as food in the worm bin,
but generally the castings are alkaline, making them ideal for adding to
annuals, the vegetable garden and most indoor potted plants.
The Meadowlark staff applies the finished worm castings as a top dressing
in the amount of about 20% of the volume of the pot. For a 4 -inch pot
Meadowlark staff add a couple of tablespoons of the compost.
Homeowners can add 20 to 25% vermicompost to potting soil. For plant
seedlings in a much smaller pot or tray, a compost tea can be added when
watering. To make the tea, add a cup of castings to a bucket of water, let it
sit for an hour or so, and then drain off the tea. As with many gardening
tasks, it is not necessary to worry too much about precise measurements. I
have a less scientific approach to distributing my compost, using it as a top
dressing for my garden plants outside. My harvest is usually small so I am
adding only a handful of vermicompost as top dressing to shrubs and
around annuals.
Becoming a Vermiculturalist
Any gardener can reap the benefits of vermicompost with just three things:

1. Some Eisenia Fetida worms,
2. A bin or container to house the worms, and
3. Appropriate kitchen scraps
Getting the worms. The Eisenia Fetida can be purchased from internet
sources if no local sources are available. Be certain, though, to purchase
only worms with the scientific name Eisenia Fetida. While these worms are
sometimes called red wigglers or compost worms, other worms may also
carry these monikers, so to be certain use the Latin name. The worms can
be sent through the mail.
The quantity of worms required to set up a vermiculture bin depends on the
amount of kitchen scraps available for composting and on the size of the
bin. There are commercially available bins that should come with
instructions about the amount of worms required to start composting.
The rule of thumb requires a pound of worms per cubic foot of bin space.
Setting up the bins. The worm population will increase and decrease
based on the bin conditions; the size of the living space, the temperature,
ventilation, light, moisture and how much food is available. Worms breathe
through the skin, which requires moisture, and moisture also helps with
locomotion. A bin needs a cover to keep moisture in and light out. The
worms are most active and able to reproduce at temperatures around 70
degrees F. Keep the bins in a convenient location indoors or in a garage
where the bin can be kept from freezing.
Those who plan to build a bin can find suggested dimensions and plans in
books and on the internet. Some of these sources are listed at the end of
this article, and those sources will also have formulas to figure out how
many worms would be required.
Short reports that Meadowlark Gardens has three commercial stacking
bins, each with three trays. Each tray has an open grid on the bottom of it
to promote air circulation, to allow extra liquid to drain away, and to allow
the worms to crawl up to a higher bin to find food. The trays are set on a
platform that that includes a reservoir below with a spigot to drain off any
accumulated compost tea. As the materials in the tray transform into
vermicompost, a new tray is put on top and all food is then put in the top
tray. Hungry, the worms wiggle their way to the tray with food, leaving the
tray with the finished compost behind. The staff at Meadowlark gives the

compost materials a little stir each time that food is added. The helps with
aeration and also keep the moisture evenly distributed.
When I first got my stacking bins set up, I lined the working bin with
shredded newspaper, added the worms and food and covered the food
with another layer of newspaper; either shredded or several several
unshredded sheets work, but in either case make sure that they are wet but
not dripping. The worms will eventually eat the bedding and that is a good
measure of when the vermicompost is ready to harvest. The first time I
harvested the compost, I waited too long. The bottom bin still had a few
worms in it, but the compost, rather than being granulated looked just like a
sloppy mess of mud filled with too much liquid. I had stumbled on to
vermicast. Now I watch the bins more closely, putting the new trays on
when the “working” tray is half-full and the bedding starts to be composted.
When a bin is ready to be harvested, I remove it from the stack and let it
cure in the open air.
Harvesting the vermicompost The vermicompost is ready to harvest
when the bin load looks dark and crumbly and it is difficult to see any
recognizable bits of organic matter. Depending on the worm population and
the size of the bin, this process can take from 3-6 months. Often the
harvest is more frequent, as is the case at Meadowlark bins, where a bin is
often ready for harvest in as little as 4 weeks. It is a good idea to rest the
compost before using it. The resting allows any eggs to hatch so that the
new worms can be added back to the compost bin. At Meadowlark the
policy is to keep the worms in the bin doing their job rather than releasing
them into the garden beds where they might disturb the local worm
populations and where they are likely to die in winter freezes.
Feeding the worms A half a pound of kitchen scraps a day can feed a
pound of worms. When scraps are added to the bin, more shredded
bedding or pages of wet newsprint should also be added to cover the food.
This keeps down odor and also reduces or eliminates the presence of flies.
At Meadowlark, staff members bring in kitchen scraps for the worms on a
weekly basis. The scraps include all kinds of vegetable peelings, bread,
cereal grains and oatmeal, spoiled vegetables and fruit/vegetable rinds.
Paper products can be added if they are free of dyes or other harmful
chemicals. Tea bags and coffee grounds can be added. Scraps can be
cut into small pieces to hasten the composting process. Some who

pamper their worms have been known to put the scraps in the blender prior
to feeding the worms, and I confess that I put kitchen scraps into the
freezer, thawing them to room temperature before adding them to the bin.
With a little observation it is easy to determine the worms’ favorite food
stuffs and it quite common for me or any worm lover to eye food scraps
and to say, ”my worms would LOVE that!”
The Eisenia Fetida need calcium to reproduce. Most food scraps contain
some calcium but if the worm population in the bin does not seem to be
renewing or expanding adding some calcium to the scraps is a good idea.
One easy way is to mash or grind up clean empty egg shells. The worms
never completely compost egg shells but they can remain as part of the
vermicompost. Another option is to add a ground up teaspoon of a calcium
based antacid pill to the bin or adding a teaspoon of garden lime (calcium
carbonate, or calcium-magnesium carbonate). Be sure to avoid adding
construction lime (slake lime or quick lime) as that will poison the worms.
Since the worms have a gizzard to help grind the ingested food material,
many suggest adding, ground egg shells, rock dust or soil in small
quantities to provide grinding materials for gizzard health. I usually add
one egg shell which I mash up in my hands until it is in tiny pieces. The
egg shell turns brown and reduces in size only slightly but I think of it as
helping the worms and adding texture to my vermicompost.
I am cautious about over feeding my worms, and when I do feed them I
check to see what is gone and what is still there. I can adjust the amount
of food according to how fast it disappears. When I travel for a few weeks
I add a bit of food before I leave and I know that my worms can survive on
the bedding materials after the initial scraps are gone. I have not left them
for more than three weeks at a time. If I were to be away longer than that I
would probably find a “worm sitter” to occasionally add food to the bins.
What to avoid. According to Short, citrus fruits and rinds may be harmful to
the worms. Although onions can be added to the bins as scraps, the staff
at Meadowlark have noticed that the worms will not eat onions or any type
of protein, which tends to be smelly. Do not give worms salty scraps such
as chips. The Meadowlark worms also have had difficulty with really hard
substances such as pineapple cores. My worms, seem to prefer the same
sweet fare that I eat, although in “scrap form.” For example, they like fruit
cores with a bit of flesh hanging on them and sweet potato peels. The

worms do not process seeds, so it is not uncommon to find sprouts in the
vermicompost -- a surprise that is a sign of healthy compost. The bins
should not have any odor other than the healthy smell of fresh compost.
Worm composting has gown in popularity as the news of its benefits to
plant health and environmental stewardship expands. It takes little space
and is low cost relative to the benefits of nutrient rich compost good for
both houseplants and garden areas.
For Further Reading
Recycle with Earthworms: The Red Wiggler Connection
Third Edition, 2007
By Shelly Grossman and Toby Weitzel
Shields Publications
Eagle River, Wisconsin
Worms Eat My Garbage
Second Edition, 1982
By Mary Appelhof
Flowerfield Enterprises, LLC
Kalamazoo, Michigan
Internet sites
www.biosci.ohio-state.edu/~soilcd/
www.cityfarmer.org
www.ext.vt.edu
“Composting your Organic Kitchen Wastes with Worms”
Virginia Tech publication 442-005
May 1 2009
By Lori Marsh, Extension Engineer
Biological Systems engineering Department
Virginia Technical University
www. nvrpa.org/park/meadowlark_botanical_gardens
Laurie Short, horticulturist

www.working-worm.com
www.wormdigest.org
www.wormpost.com
www.wormwoman.com