VERMICOMPOST: WORMS DO IT - Fairfax County Master Gardeners
VERMICOMPOST: WORMS DO IT - Fairfax County Master Gardeners
VERMICOMPOST: WORMS DO IT - Fairfax County Master Gardeners
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<strong>VERMICOMPOST</strong>: <strong>WORMS</strong> <strong>DO</strong> <strong>IT</strong><br />
By Gretchen Stark, <strong>Master</strong> Gardener<br />
Worm tunnels aerate the earth, and worms feed on decaying organic<br />
matter, releasing worm manure, also called castings which are rich in<br />
nutrients for plants. In fact, Charles Darwin believed that no other living<br />
thing “has had such a profound impact on history as has the earthworm. ” 1<br />
<strong>Gardeners</strong> have long recognized the importance of worms to plant health<br />
and have sought ways to manage and increase the benefits worms<br />
provide. Managed worm composting, or vermiculture is the long<br />
established method for cultivating and harvesting the worm castings.<br />
Laurie Short, horticulturist at Meadowlark Botanical Gardens in Vienna,<br />
Virginia, is an enthusiastic advocate of worm composting. I interviewed her<br />
about the vermiculture program at Meadowlark which has been in<br />
operation since 2010. She finds it to be a low cost convenient way to<br />
recycle kitchen scraps into a nutritious, organic soil additive.<br />
The right worm<br />
There are thousands of worm species, but it is the Eisenia Fetida (also<br />
known as red worm, red wiggler, or compost worm) that has become the<br />
champion of home worm compost bins. In the right conditions the Eisenia<br />
Fetida multiplies rapidly, and each worm consumes half its body weight in<br />
decaying kitchen scraps daily.<br />
I have had worm composting in my basement since 2009 and have<br />
watched with fascination as kitchen scraps have been transformed with<br />
biological alchemy into three products:<br />
Castings. The partially decayed organic material consumed by the worms<br />
passes through a crop and gizzard, a strong muscle filled with grit, where it<br />
is further ground up making it easy for intestinal bacteria, fungus and other<br />
micro organisms to finish the decomposition process. When the worm<br />
eventually expels it, it is called a cast. The castings have calcium, potash,<br />
phosphate,and nitrogen in addition to antibacterial and insecticidal qualities<br />
that can be easily absorbed by plant roots.<br />
1 Christopher Lloyd, What on Earth Evolved? 100 Species that Changed the World (New<br />
York:Bloomsbury,2009),p.97
Vermicompost or worm compost. refers to the materials in the worm<br />
bin that include other, undigested, mostly decayed organic material and<br />
microscopic organisms. It is rich in bacteria, and enzymes and has all the<br />
benefits of the castings, too.<br />
Vermicast refers to organic material converted totally to worm castings.<br />
Since the worms have the habit of eating and re-eating all the materials in<br />
the bin, worm castings confined in a bin with worms too long will be<br />
recycled too many times and have fewer nutrients.<br />
Benefits of worm composting<br />
At Meadowlark the staff report that as a consequence of the vermiculture<br />
program, no restricted or chemical pesticides or fungicides have been<br />
needed in the greenhouse this year, although occasionally the<br />
horticulturists use organic pesticides and fungicides. The plants are<br />
healthier in the greenhouse and continue to be healthy as they are planted<br />
in the outside garden areas. The pH range for the vermicompost varies<br />
according to the acidity of the organic matter used as food in the worm bin,<br />
but generally the castings are alkaline, making them ideal for adding to<br />
annuals, the vegetable garden and most indoor potted plants.<br />
The Meadowlark staff applies the finished worm castings as a top dressing<br />
in the amount of about 20% of the volume of the pot. For a 4 -inch pot<br />
Meadowlark staff add a couple of tablespoons of the compost.<br />
Homeowners can add 20 to 25% vermicompost to potting soil. For plant<br />
seedlings in a much smaller pot or tray, a compost tea can be added when<br />
watering. To make the tea, add a cup of castings to a bucket of water, let it<br />
sit for an hour or so, and then drain off the tea. As with many gardening<br />
tasks, it is not necessary to worry too much about precise measurements. I<br />
have a less scientific approach to distributing my compost, using it as a top<br />
dressing for my garden plants outside. My harvest is usually small so I am<br />
adding only a handful of vermicompost as top dressing to shrubs and<br />
around annuals.<br />
Becoming a Vermiculturalist<br />
Any gardener can reap the benefits of vermicompost with just three things:
1. Some Eisenia Fetida worms,<br />
2. A bin or container to house the worms, and<br />
3. Appropriate kitchen scraps<br />
Getting the worms. The Eisenia Fetida can be purchased from internet<br />
sources if no local sources are available. Be certain, though, to purchase<br />
only worms with the scientific name Eisenia Fetida. While these worms are<br />
sometimes called red wigglers or compost worms, other worms may also<br />
carry these monikers, so to be certain use the Latin name. The worms can<br />
be sent through the mail.<br />
The quantity of worms required to set up a vermiculture bin depends on the<br />
amount of kitchen scraps available for composting and on the size of the<br />
bin. There are commercially available bins that should come with<br />
instructions about the amount of worms required to start composting.<br />
The rule of thumb requires a pound of worms per cubic foot of bin space.<br />
Setting up the bins. The worm population will increase and decrease<br />
based on the bin conditions; the size of the living space, the temperature,<br />
ventilation, light, moisture and how much food is available. Worms breathe<br />
through the skin, which requires moisture, and moisture also helps with<br />
locomotion. A bin needs a cover to keep moisture in and light out. The<br />
worms are most active and able to reproduce at temperatures around 70<br />
degrees F. Keep the bins in a convenient location indoors or in a garage<br />
where the bin can be kept from freezing.<br />
Those who plan to build a bin can find suggested dimensions and plans in<br />
books and on the internet. Some of these sources are listed at the end of<br />
this article, and those sources will also have formulas to figure out how<br />
many worms would be required.<br />
Short reports that Meadowlark Gardens has three commercial stacking<br />
bins, each with three trays. Each tray has an open grid on the bottom of it<br />
to promote air circulation, to allow extra liquid to drain away, and to allow<br />
the worms to crawl up to a higher bin to find food. The trays are set on a<br />
platform that that includes a reservoir below with a spigot to drain off any<br />
accumulated compost tea. As the materials in the tray transform into<br />
vermicompost, a new tray is put on top and all food is then put in the top<br />
tray. Hungry, the worms wiggle their way to the tray with food, leaving the<br />
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<br />
aeration and also keep the moisture evenly distributed.<br />
When I first got my stacking bins set up, I lined the working bin with<br />
shredded newspaper, added the worms and food and covered the food<br />
with another layer of newspaper; either shredded or several several<br />
unshredded sheets work, but in either case make sure that they are wet but<br />
not dripping. The worms will eventually eat the bedding and that is a good<br />
measure of when the vermicompost is ready to harvest. The first time I<br />
harvested the compost, I waited too long. The bottom bin still had a few<br />
worms in it, but the compost, rather than being granulated looked just like a<br />
sloppy mess of mud filled with too much liquid. I had stumbled on to<br />
vermicast. Now I watch the bins more closely, putting the new trays on<br />
when the “working” tray is half-full and the bedding starts to be composted.<br />
When a bin is ready to be harvested, I remove it from the stack and let it<br />
cure in the open air.<br />
Harvesting the vermicompost The vermicompost is ready to harvest<br />
when the bin load looks dark and crumbly and it is difficult to see any<br />
recognizable bits of organic matter. Depending on the worm population and<br />
the size of the bin, this process can take from 3-6 months. Often the<br />
harvest is more frequent, as is the case at Meadowlark bins, where a bin is<br />
often ready for harvest in as little as 4 weeks. It is a good idea to rest the<br />
compost before using it. The resting allows any eggs to hatch so that the<br />
new worms can be added back to the compost bin. At Meadowlark the<br />
policy is to keep the worms in the bin doing their job rather than releasing<br />
them into the garden beds where they might disturb the local worm<br />
populations and where they are likely to die in winter freezes.<br />
Feeding the worms A half a pound of kitchen scraps a day can feed a<br />
pound of worms. When scraps are added to the bin, more shredded<br />
bedding or pages of wet newsprint should also be added to cover the food.<br />
This keeps down odor and also reduces or eliminates the presence of flies.<br />
At Meadowlark, staff members bring in kitchen scraps for the worms on a<br />
weekly basis. The scraps include all kinds of vegetable peelings, bread,<br />
cereal grains and oatmeal, spoiled vegetables and fruit/vegetable rinds.<br />
Paper products can be added if they are free of dyes or other harmful<br />
chemicals. Tea bags and coffee grounds can be added. Scraps can be<br />
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<br />
to feeding the worms, and I confess that I put kitchen scraps into the<br />
freezer, thawing them to room temperature before adding them to the bin.<br />
With a little observation it is easy to determine the worms’ favorite food<br />
stuffs and it quite common for me or any worm lover to eye food scraps<br />
and to say, ”my worms would LOVE that!”<br />
The Eisenia Fetida need calcium to reproduce. Most food scraps contain<br />
some calcium but if the worm population in the bin does not seem to be<br />
renewing or expanding adding some calcium to the scraps is a good idea.<br />
One easy way is to mash or grind up clean empty egg shells. The worms<br />
never completely compost egg shells but they can remain as part of the<br />
vermicompost. Another option is to add a ground up teaspoon of a calcium<br />
based antacid pill to the bin or adding a teaspoon of garden lime (calcium<br />
carbonate, or calcium-magnesium carbonate). Be sure to avoid adding<br />
construction lime (slake lime or quick lime) as that will poison the worms.<br />
Since the worms have a gizzard to help grind the ingested food material,<br />
many suggest adding, ground egg shells, rock dust or soil in small<br />
quantities to provide grinding materials for gizzard health. I usually add<br />
one egg shell which I mash up in my hands until it is in tiny pieces. The<br />
egg shell turns brown and reduces in size only slightly but I think of it as<br />
helping the worms and adding texture to my vermicompost.<br />
I am cautious about over feeding my worms, and when I do feed them I<br />
check to see what is gone and what is still there. I can adjust the amount<br />
of food according to how fast it disappears. When I travel for a few weeks<br />
I add a bit of food before I leave and I know that my worms can survive on<br />
the bedding materials after the initial scraps are gone. I have not left them<br />
for more than three weeks at a time. If I were to be away longer than that I<br />
would probably find a “worm sitter” to occasionally add food to the bins.<br />
What to avoid. According to Short, citrus fruits and rinds may be harmful to<br />
the worms. Although onions can be added to the bins as scraps, the staff<br />
at Meadowlark have noticed that the worms will not eat onions or any type<br />
of protein, which tends to be smelly. Do not give worms salty scraps such<br />
as chips. The Meadowlark worms also have had difficulty with really hard<br />
substances such as pineapple cores. My worms, seem to prefer the same<br />
sweet fare that I eat, although in “scrap form.” For example, they like fruit<br />
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<br />
vermicompost -- a surprise that is a sign of healthy compost. The bins<br />
should not have any odor other than the healthy smell of fresh compost.<br />
Worm composting has gown in popularity as the news of its benefits to<br />
plant health and environmental stewardship expands. It takes little space<br />
and is low cost relative to the benefits of nutrient rich compost good for<br />
both houseplants and garden areas.<br />
For Further Reading<br />
Recycle with Earthworms: The Red Wiggler Connection<br />
Third Edition, 2007<br />
By Shelly Grossman and Toby Weitzel<br />
Shields Publications<br />
Eagle River, Wisconsin<br />
Worms Eat My Garbage<br />
Second Edition, 1982<br />
By Mary Appelhof<br />
Flowerfield Enterprises, LLC<br />
Kalamazoo, Michigan<br />
Internet sites<br />
www.biosci.ohio-state.edu/~soilcd/<br />
www.cityfarmer.org<br />
www.ext.vt.edu<br />
“Composting your Organic Kitchen Wastes with Worms”<br />
Virginia Tech publication 442-005<br />
May 1 2009<br />
By Lori Marsh, Extension Engineer<br />
Biological Systems engineering Department<br />
Virginia Technical University<br />
www. nvrpa.org/park/meadowlark_botanical_gardens<br />
Laurie Short, horticulturist
www.working-worm.com<br />
www.wormdigest.org<br />
www.wormpost.com<br />
www.wormwoman.com