Worm real estate can take many forms, as long as the environment meets their basic needs. For short-term projects or observations, plastic soda or milk bottle bottoms do nicely. Standard store-bought plastic storage boxes or rubber containers with lids or commercial bins are suitable for more extended projects. Some worm farmers prefer to build wooden bins, because wood transfers moisture better than plastic or rubber.
Your bin size will affect how much food you process per week. Generally, allow one square-foot of surface area per pound of scraps per week. Regardless of the container you choose, be sure to include holes for aeration and drainage. To start, drill 8 to 15 holes in the bottom, depending on the container size. Many worm farmers also drill holes in the side near the top edge to further enable air flow. (Some believe that holes 1/4-inch in diameter or less will deter fruit flies from entering.) You'll also need a lid--made of wood, rubber, hard plastic, or a black plastic sheet--to maintain darkness and moisture. Raise the bin on bricks or blocks and place a tray underneath to gather excess liquid. (Consider challenging your students to test whether the liquid, in fact, is useful for plants.)
Fill your worm bin three-fourths full with damp bedding material such as shredded newspaper (1-inch strips), dead leaves, or coconut fiber (coir). This is where you'll bury food waste. Adding a handful of soil will provide the grit that worms need to digest food. Bedding materials should be moist, but not wet: about like a wrung-out sponge. Fluff up the bedding, so it doesn't become matted.
Redworms (Eisenia foetida), commonly known as red wigglers or manure worms, are the species most likely to survive relatively warm classroom temperatures. The worms that typically reside in soil tend to prefer the cooler temperatures found down under. One pound of worms (approximately 1000!) will process 3 to 4 pounds of food scraps per week. Adjust your worm count to your students' predictions of the volume of food you will generate.
You can obtain redworms through our Gardening with Kids print or online catalog (www.kidsgardening.com). For a comprehensive list of small and bulk quantities of worms, visit the links on the Worm Digest Web site (www.wormdigest.org).
Worms can "eat" their own weight in food scraps every day. Keep it vegetarian, providing vegetable and fruit scraps, pulverized egg shells (for calcium), spoiled food, coffee grounds, and tea bags. Avoid meats, dairy products, and oily foods, which can create foul odors or attract flies or rodents.
Locate worm bins in the classroom or outdoors. In either case, temperatures should remain between 40o and 80 oF. If bins are outdoors, keep them out of hot sun and heavy rains.
Being Bin Guardians
Have your young scientists feed the worms slowly at first, gauging whether the food balance and moisture content seem adequate or need to be adjusted. A popular strategy is to divide your bin into 5 to 7 sections, then bury the food in a different section of the bedding each week. The worms will follow their nourishment around the bin.
After two to three months, when most of the food and bedding have been transformed into dark, rich compost, you'll need to separate the worms so they don't suffer. One method is to move the finished compost to one side of the bin, then place fresh bedding and food waste in the other side and let the worms migrate naturally, over time, to the fresh food and bedding. You can also dump the entire bin contents onto a plastic sheet and allow students to separate the worms manually. (Help your students identify and preserve lemon-shaped cocoons, which contain between two and twenty baby worms!) As your worms continue to reproduce, you should have enough to fill another bin, pass on to other classrooms wanting to dig in, or to transfer to the school garden.
Worm Anatomy 101
Simple though they seem, worms possess some very complex attributes. Consider this: they're both male and female, reproductively speaking. The wide band, or clitellum, around their middles, covers their reproductive organs. When two worms facing opposite directions seem to be joined at this spot, they're actually fertilizing each other's eggs. They take oxygen in through their moist skin. And they can't see, but move away from light. (This brilliant response protects them from drying out in the sun and becoming food for predators.) They do have a front and behind end (the narrower, pointed end faces forward), and they use their bristly segments, which are surrounded and connected by muscles, to move forward and to stay put! (The setae or bristles on the segments force robins to work hard for their lunches!) What can your astute observers discover about how worms work by using their naked eyes or hand lenses?
Easy to raise, worms provide a free and hassle-free source of rich fertilizer. What's more, they engage students' hands and minds and teach basic environmental concepts. To start your own classroom worm farm, you'll need an aerated container, bedding (such as shredded newspaper), a moist and temperate environment, a small amount of soil, and red wigglers.