Composting with Worms

Earthworms transform organic matter in your garden soil into nutrient-rich humus that plants can use. People typically think of earthworms as outdoor creatures, but you can actually raise them indoors, too, and use their castings to improve your soil indoors and out. Why bother? Because earthworm compost or "castings" contain five times more nitrogen, seven times more phosphorus, and 11 times more potassium than regular garden soil. The castings also contain microbes that can help plants fight disease.

Earthworm Composting is known as Vermicomposting
You can use the rich worm castings in the garden, or in container potting soils. Plus, raising worms indoors is a fun winter project and a way to recycle vegetable scraps from the kitchen. If you think earthworms don't produce a lot of compost, consider that the average red wiggler worm consumes its weight in kitchen scraps daily. Multiply that by a couple hundred earthworms and you've got a compost factory!

You can build your own worm bin or buy a commercial product. Bins can be plastic or wood. If you're building your own, make it as large as is manageable in your space but only 8 to 12 inches deep. Earthworms feed on the top layers of the bedding.

Drill 8 to 12, ¼-inch-diameter holes into the bottom and sides of the bin for proper aeration and water drainage. Drill more holes if you are using plastic or if the bedding stays consistently wet. Place a tray under the bin to collect the earthworm "tea" that drips from the bin. This tea makes an excellent foliar fertilizer for houseplants.

The Bedding - Your worms need more than just the occasional banana peel or leftover lettuce leaves to thrive. They need a bedding material that will retain moisture while providing food, air, and a home for the young wigglers. Some good options are shredded cardboard, newspaper, or coir (coconut husks); and peat moss. Moisten the bedding before placing it in the bin and wring it out until it has the wetness of a well-wrung sponge. Place 4 to 6 pounds of bedding in a 4-foot-square worm bin. Fluff and occasionally mist the bedding with water if it appears dry.

Loosely cover the bins to keep earthworms in the dark. They need temperatures between 40°F and 80°F to survive, so place the bins in a cellar, warm garage, or even under the kitchen sink!

The Worms - Although all earthworms eat organic matter, the best type to use in vermicomposting is red wiggler worms. Red wigglers thrive in temperatures between 55°F and 77°F — just like most homes.

The Food - Feed your worms vegetable scraps, fruit peels, coffee grounds, tea bags, crushed egg shells, and even leftover pasta. Worms don't like garlic, onion, and spicy foods. Also, avoid adding meats, fish, fatty and oily foods, and bones. Chop up the scraps into small pieces and lay a thin layer on the top of the bedding. The worms will come up to feed in the dark. Add a small amount of gritty material such as potting soil or cornmeal to help your worms digest their meal.