How to Start a Compost Heap
A compost heap turns everyday garden and kitchen waste into a dark, crumbly soil improver. It need not be complicated or perfectly managed. Start with a convenient spot, add a sensible mix of materials, and let air, moisture and soil organisms do the work over the coming months.
Choose a level, sheltered place with bare soil beneath the heap or bin. Direct contact with the ground allows worms and other helpful organisms to enter, while drainage prevents a soggy base. Pick somewhere you can reach easily in wet weather, ideally near the kitchen route or allotment path, but not where it blocks access. A wooden bin, recycled-plastic bin or simple open heap can all work well. Aim for at least 1 m by 1 m if space allows, as a larger volume holds warmth better. If rats are a concern, use a sturdy bin with a lid and avoid putting cooked food, meat, fish, dairy products or oily scraps into it.
Gather a balance of green and brown materials before building up the heap. Greens are moist, nitrogen-rich materials such as grass clippings, vegetable peelings, tea leaves, coffee grounds and young weeds without seed heads. Browns are drier, carbon-rich materials such as torn cardboard, autumn leaves, prunings, straw, woody shreddings and scrunched paper. A useful starting approach is to add roughly two buckets of browns for every bucket of greens, although there is no need to measure precisely. Tear or chop bulky pieces to speed breakdown. Avoid glossy paper, plastic-coated packaging and invasive weeds with persistent roots, as these can survive or contaminate the finished compost.
Start with a loose layer of twiggy prunings, coarse stems or shredded woody material to improve airflow at the bottom. Then add alternating handfuls or layers of greens and browns, mixing lightly as you go. Thin layers are better than large slabs of grass clippings, which can turn slimy and exclude air. Add a few shovelfuls of ordinary garden soil or finished compost if available; this introduces useful organisms but is not essential. Keep adding material whenever you have it, rather than waiting to fill the bin at once. If you have a large autumn leaf collection, make leaf mould separately in a bag or wire enclosure, as leaves break down more slowly than mixed compost.
Check moisture whenever you add a substantial amount. The contents should feel like a wrung-out sponge: damp enough for decomposition, but not dripping. In dry spells, water lightly with a watering can or saved water from a water butt. During prolonged rain, fit a lid or cover the top with old compost bags held down with stones, while leaving some ventilation. If the heap smells sour, looks wet and clumped, mix in dry shredded cardboard, straw or leaves. If it is dry and unchanged, add moist green material and water gently. These small adjustments matter more than achieving a perfect recipe.
Turn the heap after several weeks or when it has settled noticeably. Lift material from the outside into the centre and bring the warmer middle layers outward, using a garden fork. This introduces oxygen and mixes materials at different stages of decay. A heap may warm noticeably after turning, especially in late spring and summer, but a cool heap can still make good compost more slowly. Turn it once or twice if you can, but do not worry if time is limited. At an allotment, covering a heap between visits helps maintain moisture. Wear gloves and take care around forks, particularly where hedgehogs may have sheltered near the base.
Your compost is ready when it is dark, earthy-smelling and mostly crumbly, with only a few recognisable woody pieces left. This often takes six to twelve months, depending on the season, materials and how often it is turned. Sieve it if you want a fine texture for seed beds, returning larger fragments to the heap. Spread finished garden compost 3 to 5 cm deep over beds in autumn or spring, then let worms draw it in. Use coarser compost as mulch around established plants. Do not rely on homemade compost alone for every nutrient need, but use it regularly to improve soil structure and moisture-holding capacity.
Frequently asked questions
Can I compost weeds from my garden?
Yes, but choose carefully. Young annual weeds without flowers or seed heads are usually fine, especially if mixed through a warm, active heap. Avoid invasive roots and mature seed heads unless you are certain your heap gets hot enough to destroy them. Put those in local green-waste collections where available.
Why is my compost heap not getting hot?
A cool heap is not necessarily failing. It may simply be small, dry, short of green material or not yet full enough to retain warmth. Mix in moist greens, add shredded browns for balance, water lightly if dry, and turn it. It will still compost, though usually more slowly.
How often should I turn a compost heap?
Turn it when you can, rather than treating it as a strict chore. One turn after the heap has settled and another later in the season can speed decomposition noticeably. If you cannot turn it, keep adding a balanced mix and maintain gentle moisture; usable compost will still form over time.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 18 Sep 2026.