Compost is one of the best organic fertilizers for introducing nutrients and beneficial microbes to your soil, but many gardeners do not have the space or time to maintain a traditional compost pile. A vermicomposter, or a composter that uses worms, is an economical, time saving and space saving solution.
Worm castings are full of beneficial microbes and nutrients which make an ideal plant fertilizer for houseplants, and for food plants in containers and gardens. Only red wigglers, or (Eisenia fetida or Eisenia foetida), should be used for composting in bins. E. fetida are also called tiger worms, redworms, and other names. Eisenia hortensis or the ‘European Nightcrawler’ is sometimes used, but these worms have different cultural requirements, and they are larger and are often sold as fish bait. Canadian nightcrawlers (Lumbricus terrestris) are often used as fish bait, but require cool conditions unsuitable for composting.
Where to Locate a Vermicomposter or Worm Composter
When deciding where to locate your worm composter, consider both your needs and the needs of the worms. A vermicomposter can be set up anywhere that it does not freeze or get too hot, including in the kitchen, garage, basement, greenhouse, or in the shade during warm weather.
The type of worms used for vermiculture need these conditions:
- Redworms thrive in temperatures between 55° and 77°F for the bedding. The temperature inside of the box is not the same as outside, and is usually lower than the air temperature. If the bedding temperature is below 50°F, worm activity slows down. Temperatures above 85°F is harmful or fatal to the worms.
- The bedding needs to be moist. Worms breathe through their skin, and cannot do so if their bedding is not moist.
- Worms breathe in oxygen and breathe out carbon dioxide, so there must be good air circulation in and around the composter.
- Worms tolerate a wide pH range from an acid bedding of 4.2 to a quite alkaline bedding (8 or higher), but they do best at a neutral pH of around 7. If your worm bedding gets too acidic, it can be corrected with lime that is available at any garden store (calcium carbonate). Do not use hydrated lime, only limestone, since it can kill your worms.
- A wide container makes a better worm bin than a deep container, since the worms hang out in the upper layers when it is dark. The larger the system, the better, so that if conditions become unbearable for your worms in one area, they have a different area with different conditions to migrate to.
Worms should be kept in a dark location since they do not have eyes and cannot see. Instead, worms have cells to sense light, which they will move away from. Worm bins should be constructed of a material that is not transparent (that you cannot see through), and should have a lid that prevents light from entering. In a dark bin, worms stay on the surface, actively feeding on material. If you do not have a bin that excludes light, line both the inside and outside of the bin with a paper to keep any light out.
Worms must have fresh air to breathe, so your worm bin will need several holes in the top for aeration. You can drill 5 to 7 holes that are 1/4 to 1/2 inch wide using a drill bit. Your container will also need holes drilled in the bottom.
Your worm composter will need to be propped up on feet for two reasons: so that the worms will not try to escape and so that excess moisture can drain. Four small wooden blocks or other objects that are about 3 inches high can be attached to the bottom of the bins. So that the bin will only drain out of one hole, make one foot smaller and drill a hole in the corner near the smaller foot.
Vermicomposter or Worm Composter Bedding
Your worms will also need bedding which can be made out of shredded fallen leaves, shredded newspapers, shredded office paper, or other paper that is not glossy. Avoid shiny newspaper inserts and other colored paper. You can also use peat moss, but make sure to leach it with plenty of water or it will be too acidic for worm bedding. Coconut fiber, shredded paper egg cartons, shredded brown paper bags, or shredded plain brown cardboard will also work. Make sure there are no clumps of bedding material. Keep adding bedding over time to keep bin conditions ideal.
Fill the bin about two thirds full of fluffy bedding material, and then add water until the bedding is about as moist as a wrung out sponge. The bedding serves as a home for the worms and also a place to bury food scraps so they will not cause odors. Now the bin is ready to add worms.
How to Start a Vermicomposter or Worm Composter
You can start with a pound of worms, which will be about 1,000 worms. You can start out with fewer worms, but it will take longer for your bin to produce compost, so plan on the worms maturing and reproducing in a few months.
Adult worms in an ideally managed bin can eat up to their body weight or more of food scraps daily, but plan on them eating ¼ to ½ their weight initially. When you put them in the composter, they will burrow into the bedding in 5 to 10 minutes.
The worms will reach their optimal population level within a few months. Red worms have the ability to limit their own population, so do not worry about having an overpopulation that you need to find a new home for. Barring a disaster in your bin, you will also not need to repopulate your bin with new worms, either.
Worms will not usually try to get out of the bin because they prefer the dark moist home that you have provided. If your worms are trying to escape, make sure their bedding is not too wet or dry, and is about as wet as a wrung out sponge. Depending on what food your worms were raised, they may have an initial preference for one type of food, but most worms like coffee grounds. It may take a few weeks for your worms to acclimatize themselves, during which period they will not eat as much.
What to Feed Worms in a Vermicomposter or Worm Composter
Feed your worms anything organic, including fruit peelings, vegetable peelings, grains, coffee grounds, coffee filters, and shredded newspapers. Avoid feeding them too much citrus peels, especially if the peels have been pulverized. You can feed them whole citrus peels, but the peels break down slowly, so if your bin starts to smell moldy, remove some of the peels and save them for a future feeding.
Worms will eat meat and dairy products, but adding these to your bin also encourages rodents, so either avoid adding animal products or make your bins so that rodents cannot enter. Oils, meat, and dairy also increase the chance of creating an odor problem.
Since worms do not have teeth, they will benefit from adding gritty foods to the bin, such as ground up eggshells or a little gritty soil. Worms, like birds, have gizzards to grind up food, and the grit helps the worms’ bodies to break down scraps. Worms actually eat the microbes, but in the process eat the food the microbes are living on. The microbes break down scraps so that it is ready for the worms to eat. You are likely to find other beneficial organisms in a healthy bin, such as springtails and mold, which help to break down scraps for the worms to eat faster.
Fibrous foods like carrot peels, broccoli stalks, and potato peels take longer to break down. Pureeing or chopping these scraps into small bits before adding to the bin helps the worms eat them faster.
Worms in a typical bin can eat a pound of scraps daily. Mentally divide your box into four quadrants and feed your worms in a successive quadrants every day or two. To remember which quadrant you added to last, put a small plastic object or a piece of laminated paper on top of it. The worms will move into the next quadrant to follow the food. If you notice that your worms have not eaten all of the food in the last quadrant, they are being fed too much. If they have already eaten all of the food, you may want to feed them more.
Other Info about Vermicomposter or Worm Composter Worms
When red wigglers are threatened or handled roughly, they emit a strong odor via a pungent liquid. A few people are allergic to this liquid.
Each worm has both female and male reproductive organs, but two worms are still required to reproduce. The worms lay eggs in cocoons, which contain several eggs each. The cocoons are round to tear-drop shaped and pale yellow when immature, and become darker as the worms inside mature. The cocoons can withstand harsher conditions than the worms themselves and can persist for many years, up to 4 decades, in the soil until the conditions are right for hatching. Letting their bedding dry out slightly can encourage hatching. Worms lay a cocoon about once and month, and adding calcium sources, such as crushed egg shells, stimulates worm reproduction.
Unless there is a problem within the unit, there is no odor. The only time odors occur is when there is an imbalance in the bin which can be caused by adding too much moist food. Add more dry bedding to absorb excess moisture.