Can I use worms dug from the garden?

Not recommended. Worms that burrow deep in soil don't like a shallow bin with a thick layer of food. Composting worms are the kind that live at the surface or under piles of organic matter; they break down waste and breed faster. Get starter worms from a grower.

Which scraps should stay out?

Meat, bones, fish, fatty or greasy food, salty or heavily seasoned food, citrus, onions, garlic, and dog, cat or human waste. Raw vegetable and fruit scraps, small amounts of coffee grounds, and crushed eggshells are safer.

Can I water leafy vegetables with worm-casting tea?

Use it on the soil. NC State Extension advises not applying it to edible plant parts unless you are certain it is free of pathogens, which matters most for vegetables eaten raw. Pour it at the base instead.

A worm bin at home: which worms, feeding, moisture and harvesting castings

One worm bin turns kitchen vegetable scraps into worm castings, a crumbly fertiliser that mixes well into potting soil, without the hot, turned pile of ordinary compost. Four things matter: the right kind of worm, a shady spot, bedding that is damp rather than wet, and no more food than the worms can keep up with. This lesson gives figures from Thai and overseas guides, with a worked feeding example for one basin.

If you would rather start with a regular compost pile, see making compost from kitchen scraps.

Choosing the right kind of worm

Earthworms fall broadly into two groups: those that burrow deep into the soil, and those that live at the surface or under decaying organic matter. The second group breaks down organic matter better and breeds faster, so they are the ones used for composting.

Species	What the sources say
AF, African nightcrawler (Eudrilus eugeniae)	called a commercial strain in Thai research; large, averaging about 1.7 g per worm in one trial
Pheretima peguana	used in Thai research; in the same trial much smaller, about 0.2 g per worm, and adapted less well to that bedding than AF
Perionyx sp.	cited as a Thai strain in a Maejo University review
Red wiggler (Eisenia fetida)	the standard species in U.S. guides; prefers about 15-25°C

As a beginner, get starter worms from a grower who can tell you the species. Don’t dig them from the garden or use fishing bait worms.

Container and location

A basin about 50 cm across, with about 20-30 drainage holes in the bottom. For more, Thai growers use concrete rings 80-100 cm across.
Keep it in the shade, out of strong sun and rain.
Keep predators out. Ants, geckos, toads and skinks readily eat surface-dwelling worms; cover the bin with mesh.

NC State Extension sizes a bin at 1 square foot (about 30 x 30 cm) of surface per pound (about 450 g) of food scraps a week, 20-50 cm deep, with air holes in the upper sides near the lid.

Bedding

Bedding is where the worms live. Two kinds are common.

Cow manure, the usual choice among Thai growers. Soak it in water for 1-2 nights and drain it, three times over, which takes about 7 days. This cools it; fresh manure is still hot and full of gas, and worms cannot live in it. Drain until just damp and fill the basin 15-20 cm deep.

Paper and leaves, as in the NC State guide. Tear newspaper, paper bags or cardboard into strips about 1 cm wide, soak for 5-10 minutes, wring them out, fill the bin about halfway and mix in a handful of good soil. Avoid glossy paper and magazines.

Put the worms on top and watch. If they burrow in on their own, the bedding is fine. If they refuse, the manure usually hasn’t been soaked long enough or has cleaning chemicals from the stall in it.

Moisture and temperature

Worms that live under manure or decaying matter do best at about 70-80% moisture; NC State gives about 80%. The easiest check is to squeeze a handful of bedding: only 2-3 drops should come out. A stream means too wet; no drops means too dry.

A Thai guide suggests misting when the surface dries out, roughly every 1-2 days depending on the weather, without letting it get soggy, or the worms will leave the bin.

The suitable range is about 15-28°C, and tropical worms tolerate heat better than temperate ones. A Thai hot season easily goes above that, so keep the bin in shade with a breeze, away from walls that take the afternoon sun, and don’t seal it with a solid lid that traps heat.

Squeeze the bedding: 2-3 drops is the moisture worms like. Check it every time you feed.

How much to feed: one basin, worked out

Sources disagree quite a bit, so start low and work up.

Thai guide: green vegetable scraps and weeds at 120-150 g per kg of worms per day, doubled for foreign strains.
NC State: 1 lb of worms eats up to 2 lb of scraps a week, roughly 285 g per kg of worms per day.

Example. A 50 cm basin stocked with 300 g of worms (the Thai guide suggests 250-300 g per basin).

Low figure: 0.3 kg x 120-150 g = 36-45 g a day, about 250-315 g a week.
High figure: 0.3 kg x 285 g ≈ 86 g a day, about 600 g a week.
Start at about 250 g a week. Chop scraps small, spread them no more than 2.5 cm deep, and cover with 2.5-5 cm of bedding.
Add the next lot only when the last one is nearly gone. If they finish it quickly, move gradually toward the high figure.

The Thai guide notes that in about 4-6 weeks the number of worms roughly doubles, so the amount of food grows with it.

Good to add	Keep out
vegetable scraps, fruit peels	meat, bones, fish
coffee grounds, tea bags (a little at a time)	fried, greasy or fatty food
crushed eggshells	salty or heavily seasoned food
fresh leaves and weeds	citrus, onions, garlic
paper coffee filters	dog, cat and human waste

From bedding prep to sieving castings, for a cow-manure basin

Harvesting castings

With cow-manure bedding, the Thai guide says that after about 45 days the bedding has all turned to castings: small oval pellets, rather like tiny rugby balls. A paper-bedded bin like NC State’s takes about 4 months.

Ways to separate the worms from the castings:

Stop watering for about 7 days so the castings dry and sieve easily.
Sieve through a basket or screen with holes the castings pass through but the worms don’t.
Let the worms move. Feed only one side of the bin for several weeks; the worms migrate there, and you scoop castings from the empty side.
Use light. Tip the bin onto a plastic sheet in bright light. The worms burrow down away from it; scrape off the top layer about every 5 minutes.

Watch for egg capsules, lemon-shaped and about the size of a match head, and put them back in the bin with the worms.

Mix the castings into potting soil or spread them around plants, then cover with soil or mulch. Don’t leave them in the sun.

Worm castings are for the soil, not for pouring over leaves you will eat raw.

Problems and fixes

Symptom	Usual cause	Fix
Bad smell	overfeeding, too wet, exposed food, not enough air	stop feeding for 2 weeks, add dry bedding, bury food, drill more holes
Flies	exposed or rotten food, too much food	always bury food, no rotten scraps, feed less
Worms escaping	too wet, too hot, or unsuitable food	fix moisture and location first
Liquid in the bottom	overwatering or very watery scraps	add dry bedding, cut back on juicy fruit
Worms dying	too dry or wet, too hot, too little air or food	move to cool shade, adjust moisture, add food and bedding

Common mistakes

Using fresh cow manure straight away. It is still hot and gassy; worms die or flee.
Feeding a lot at once. Food rots before the worms get to it, and the smell follows.
Not burying the food. Flies lay eggs in it.
Putting the bin in the sun or the rain. It overheats or floods.
Using worms dug from the garden. Wrong group; they won’t live in a bin.

Sources

General information, not medical advice. If you are pregnant, take regular medication, or have a liver or kidney condition, ask a doctor or pharmacist before taking herbs beyond normal food amounts.