How to Build a Wormery

Why a Wormery?

A wormery — also called a vermicomposter — uses red brandling worms (Eisenia fetida) rather than the common earthworm to rapidly digest kitchen waste. The result is worm castings: an extraordinarily fertile, fine-textured compost that has higher levels of available nitrogen, phosphorus, and potassium than conventional compost, and a liquid "worm tea" that diluted and applied as a feed is one of the best liquid fertilisers available.

A wormery is ideal for small gardens, flats, and anyone who generates more kitchen waste than a conventional compost heap can handle. It takes up minimal space and, if managed well, produces no smell.

Building a Simple Wormery

A wormery can be bought ready-made or made from two stacking plastic boxes:

1. Take a large opaque plastic box with a lid. Drill drainage holes in the base and ventilation holes around the upper sides.
2. Place this inside a second, identical box to catch liquid drainage — this is your worm tea.
3. Add 10cm of bedding material: torn cardboard, damp newspaper, or coir. This should feel like a wrung-out sponge.
4. Add your worms — at least 500g of red brandlings. These are not garden earthworms; they must be the surface-dwelling species available from fishing suppliers or wormery retailers.
5. Add a thin layer of kitchen scraps and cover with a piece of damp cardboard or newspaper.

What to Feed

Yes: Vegetable and fruit peelings, coffee grounds, tea bags (staple-free), eggshells, bread in small amounts, crushed cardboard.

No: Meat, fish, dairy, citrus in large quantities, onion in large quantities (acidic, worms dislike it), anything cooked in oil, glossy paper.

Managing the Wormery

Keep the wormery in a sheltered spot — worms are most active between 15–25°C and will die if frozen. In summer, keep it in shade. In winter, insulate it with old carpet or bubble wrap or bring it into a garage.

Feed little and often — a handful every 2–3 days is better than a large dump weekly. If the wormery smells, it is too wet or has too much nitrogen-rich material: add more torn cardboard and reduce feeding temporarily.

Using the Outputs

Worm castings can be used as a seed compost, potting compost additive, or top-dressing around plants. The liquid that collects in the base should be diluted 10:1 with water before use as a liquid feed — undiluted it can scorch roots.

Worms in the Garden

Red brandlings do not thrive in open soil — they are surface-dwellers, not deep burrowers. However, spent wormery compost added to the garden carries millions of bacteria and fungi that genuinely improve soil biology.