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Spokane, Washington  Est. May 19, 1883
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Worm bin works wonders

Pat Munts Correspondent

Are you still on your new healthy diet? Are the veggie and fruit trimmings piling up in the garbage can? Want another reason to stay on your diet? Make black gold by starting an indoor worm bin.

Its easy says Chris Koehler, a WSU Spokane County Extension Educator and Master Composter who has maintained a worm bin for years.

Bin basics

You will need a wooden, opaque plastic or metal container with a lid to house your worms. It needs to be about eight to 12 inches deep, about 1 by 2 feet in size and light-proof. Drill quarter-inch holes two to three inches apart in the bottom. Place the box on blocks of wood on a tray so excess moisture can drain. Koehler uses both a plastic storage box and a wooden bin but likes wood better because it’s easier to manage moisture levels.


Your worms will need moist bedding of shredded newsprint (black ink only), shredded corrugated cardboard, peat moss or leaf mold. Koehler uses newsprint because; “It’s free and easy (to use).” The bedding needs to be kept as moist as a wrung out sponge. The bin should be about half full of bedding.

The worms

Red worms (Eisenia foetida) also known as red wigglers or manure worms are the best worms for a bin. They are surface feeders that don’t need deep soil like their garden cousins. Start with two pounds of worms for every pound of scraps you generate daily. Once established their population will increase or decrease depending on how well they are fed.

What to feed

Anything that can be composted can go into your worm bin: vegetable and fruit scraps, well-crushed egg shells, coffee ground and filters and tea bags. “Try to avoid citrus,” Koehler suggests. “The citrus oils can be toxic to the worms.” Feed them regularly by placing food into the bedding at a different spot each time. It is better not to add large quantities of food at one time but spread it out over a few days.

Bin maintenance

Your bin needs to be where you can easily put in your trimmings but where the worms won’t freeze; 55 degrees to 77 degrees is perfect. You will need to add new bedding periodically and check moisture levels a couple of times a week. Properly cared for bins do not smell or harbor fruit or house flies.

Harvesting black gold

Once your worms start producing castings, they can be harvested. Move the food and uneaten bedding to one end of the box and give the worms a couple of weeks to move to that area. Then scoop out the black castings at the other end, remove any remaining worms and use your black gold to top-dress house plants, seedlings or make compost tea.

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