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Organic gardeners know that worms help plant matter to decompose, improve soil structure and leave behind rich fertilizer. Researchers have now found that worm composts actually make plants grow faster.
Researchers at Ohio State University found that including just 10 to 20 percent worm compost (by volume) in a commercial potting mix can boost the growth rate of marigolds, bachelor's buttons, tomatoes and peppers by up to 40 percent over that of plants grown in an unamended mix.
"Even when we provided all plants with enough fertilizer for optimum growth, plants still grew better when the soil was amended with worm compost," reports Jim Metzger, Ph.D., horticulture professor at Ohio State.
Researchers at Mississippi State University have found that worm compost increases the germination rate and growth of cucumbers. And scientists in Italy have confirmed similar results with carrots.
How can you get the powerful benefits of worm castings in your garden? If your home compost pile already contains lots of worms, you give your plants a boost every time you apply the compost.
Don't have a compost pile? You can set up a worm bin in your home, feed the worms your kitchen scraps and collect their castings. Here are some hints, from Amy Stewart, author of "The Earth Moved: On The Remarkable Achievements of Earthworms" (Algonquin Books, 2004).
The worms that live in your outdoor compost pile may not be the best species for a closed worm composting system. Some worms, like nightcrawlers, will not survive long in captivity. Your best bet is to order worms from a reputable worm dealer. Eisenia fetida or E. andrei are generally considered the best species of worms for composting.
You can buy a worm bin (check our "Find Organic Gardening" section for links to lots of companies that sell worms, bins and other supplies), or build your own from a plastic tub with a tight-fitting lid. Be sure to include holes for air and drainage, and put a fine mesh screen in the bottom to keep the worms from escaping.
Feed worms a low-fat, vegan diet: they love fruit and vegetable scraps, coffee grounds, tea bags, rice, pasta, and bread, but they can't tolerate meat, dairy, or oil.
Keep the food covered with a layer of shredded newspaper or cardboard, which will keep flies away and provide another food source for the worms.
Add crushed eggshells to prevent acidity. The worms will not eat the shells—you can add them to your garden along with the castings.
Keep the bin as damp as a wrung-out sponge. Adding wet or dry newspaper is a good way to change the humidity in the bin.
Keep your bin in a sheltered spot, away from sun and rain. Worms prefer a moderate climate, 60 degrees F is ideal. A small worm bin will even fit in your garage or cellar.
Be patient! It can take up to six months or a year before you collect castings from your bin for the first time. It takes the worms this long to get acclimated and start reproducing enough to fill the bin.
