The mix: browns and greens
Woodchip is a "brown": lots of carbon, little nitrogen. On its own it rots slowly. To speed it up, mix in "greens" rich in nitrogen: grass cuttings, fresh manure, chicken litter, kitchen scraps, or comfrey and nettle leaves.
A rough guide is two or three parts chip to one part greens by volume. If the heap smells, add chip; if it stays cold and dry, add greens and water.
Hot heap or cold pile
- Hot: build a heap at least a metre each way in one go, wet it like a wrung-out sponge, and turn it every week or two. It heats up, and can be ready in four to six months.
- Cold: tip the chip in a corner, wet it, and leave it. In one to two years the inside is compost. Summer loads with plenty of leaves rot fastest.
Using it
Rotted chip is ready when it's dark, crumbly and smells of woodland. Sieve out the big pieces and put them back in the next heap. Use it as a soil improver dug into beds, a top dressing, or a potting mix base once sieved fine.
Tip: A fresh load can get hot in the middle within days. That's the rot starting, not a problem.