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SUS Farms · Utah Gardening
Worm composting (vermicomposting)
soil · intermediate · ~6 min read
Red wigglers (Eisenia fetida) eat half their body weight in food scraps every day and produce castings — the most concentrated, biology-rich fertilizer most home gardeners never try. A single 3-tier worm bin under the kitchen sink processes a household's vegetable scraps and yields a 5-gallon bucket of castings every 3–4 months.
The bin setup
Stacking-tray bins (Worm Factory, Hungry Bin) are the easiest entry point — about $100 for the kit. DIY: 2 plastic totes, 1/4" holes drilled in the bottom of one, nested inside the other. Worms migrate up to the new feeding tray, leaving finished castings below for harvest.
What to feed
Yes: vegetable scraps, fruit peels, coffee grounds, eggshells (crushed), tea bags, bread, plain rice/pasta. Bedding: shredded newspaper, cardboard, dried leaves. No: meat, dairy, onion or garlic in quantity, citrus peels (too acidic), oily food, anything salted. Cut food into small pieces — surface area determines processing speed.
Maintenance rhythm
Feed once a week. Bury food under bedding to discourage fruit flies. Bedding should feel like a wrung-out sponge. Add fresh bedding when you see worms instead of bedding at the surface. Drain the leachate (worm tea) from the bottom tray weekly — dilute 1:10 and use as liquid fertilizer.
Harvesting castings
When the bottom tray is mostly black with no recognizable food, it's done. Pull it off, dump on a tarp in sunlight — worms migrate down away from the light, you scrape off the top, repeat until you've separated worms from castings. The casting product looks and smells like fresh forest soil.
Using the castings
Mix 10% by volume into seed-starting mix — boosts germination and seedling vigor. Side-dress vegetables: 1 cup per tomato plant. Brew worm-casting tea (1 cup castings in 5 gallons water, aerate 24 hours) for foliar feeding. The biology is more valuable than the NPK numbers.