Worm compost is a nutrient-rich, natural fertilizer and soil conditioner - a valuable asset here in Colorado! Instead of buying compost, you can grow your own at a fraction of the price. Worms can use items that might otherwise go to waste – old veggies, bread heels, even coffee grounds.
What do you need to build a worm bin?
- A wood or plastic bin (not metal) - A good size is 1.5’H x 2’ D x 3’W. Drill air holes in the top and drainage holes in the bottom, ¼” or smaller.
- Moist bedding – Shredded newspaper, leaves, straw are all useful if kept as moist as a wrung-out sponge. The bedding should be changed once or twice a year, or if there are any problems. Add about 8” of moistened bedding to bottom, place worms inside and leave the lid off so that they will work down into the bin away from the light.
- Food – Worms like fruit, vegetables, coffee grounds, bread and leaves. Don’t use any animal products or oils. Also avoid onions and citrus fruits; you may find that earthworms try to escape the strong odors from these! To feed your worms, dig a hole at least 3” deep in the bedding, dump food in and cover with more bedding. Pick a new spot each time you add food. Adding a handful of well-crushed eggshells every few months provides grit and calcium for your worms.
- Moisture and warmth - Earthworms like moderate temperatures. Putting your new bin in a location like a basement, garage or laundry room can prevent the worms from overheating or freezing. If the bedding seems dry, add water a little at a time. If there is excess water, be sure that the bin can drain. In cold weather, your bin should be covered with plastic or a tarp.
- Worms - Brandling worms (Eisenia foetida) and red wigglers (Lumbicus rubellus) are the most common worms found in worm compost. These can be purchased online at www.gardensalive.com. We don’t recommend bringing earthworms from your garden into a worm compost bin. These worms are a different species and don’t thrive in a bin environment.
Caring for your worms
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- Feed your new worms only a little at a time for the first few weeks to ease the transition. As your worms reproduce, you can increase the amount of food you give them. Don’t overfeed, or the food will rot, resulting in a smelly bin and unhappy worms.
- Every once in a while, check the bin for excess moisture. Too much moisture promotes the growth of anaerobic organisms, which can cause a bad odor. Wooden bins dry out faster than plastic. If the bedding seems dry, add water a little at a time. If there is excess water, be sure that the bin can drain. In cold weather, your bin should be covered with plastic or a tarp.
- Every 3-6 months, move compost to one side and put new bedding on empty side. Add food to new bedding only. Within 1 month, worms will crawl over to new bedding and the finished compost on the old side can be harvested. After removing the compost, add new bedding to “old” side.