Why a compost heap earns its place

There is something quietly satisfying about turning a pile of peelings and prunings into dark, crumbly compost. It saves you money on bagged soil improver, keeps a good chunk of waste out of your bin, and feeds your borders and pots with something far richer than anything you can buy. Best of all, it costs nothing but a little space and a few minutes each week. You do not need a large garden or expensive equipment — a corner behind the shed and a sturdy bin will do nicely.

The golden rule: balance greens and browns

Every successful compost heap is built on a simple ratio. You are feeding micro-organisms, and they need both nitrogen and carbon to thrive.

• Greens are the soft, damp, nitrogen-rich materials: fruit and vegetable scraps, grass clippings, tea leaves, coffee grounds, spent flowers and annual weeds.
• Browns are the dry, carbon-rich materials: fallen leaves, shredded cardboard, newspaper, straw, woodchip, egg boxes and cardboard tubes.

Aim for roughly equal volumes of each, or slightly more browns if you are unsure. If the heap turns slimy and smells sour, you have too much green — stir in more browns. If it sits dry and lifeless, add a few handfuls of greens and a splash of water. This single habit prevents most composting problems before they start.

Choosing a spot and a bin

Site your bin on bare soil in a sunny or partly shaded spot, so worms and soil organisms can move in from below. Avoid somewhere that stays waterlogged, and leave enough room to get a fork in comfortably.

Almost any container works. A purpose-made plastic bin with a lid is neat and keeps rain out; a slatted wooden bin lets in air; a simple three-bay pallet system is ideal if you want to turn regularly and have several batches on the go. Aim for about one cubic metre — smaller heaps dry out, larger ones are difficult to manage.

Keep a small lidded caddy by the back door for kitchen scraps and empty it every couple of days. It is the difference between composting that becomes a habit and composting that becomes a chore.

What to add and what to leave out

Virtually anything that grew in your garden will compost. Chop or shred it first — the smaller the pieces, the faster the process.

• Fruit and vegetable peelings, cores and teabags (check they are plastic-free)
• Coffee grounds, crushed eggshells and dead houseplant leaves
• Grass clippings in thin layers, never in thick mats
• Soft prunings, hedge trimmings and spent bedding plants, chopped small
• Shredded paper and card, torn into pieces
• Hair, and dust from natural-fibre carpets

Keep out cooked food, meat, fish, dairy and oils, which attract rats. Leave out diseased plants and perennial weeds such as bindweed, ground elder and couch grass unless your heap reliably gets very hot. Dog and cat waste, glossy magazines, treated timber and anything plastic should stay well away.

Keeping the heap working

Three things keep a heap active: moisture, air and warmth. Think of a wrung-out sponge — damp, not dripping. Water it during dry spells and add browns if it turns soggy.

Turn the contents every two to four weeks with a garden fork, bringing the outside to the middle. This adds oxygen, which speeds everything up and keeps smells away. A well-built heap will heat up noticeably in the centre; if you plunge a fork in and it feels warm, you know it is working.

• Smelly and slimy: too wet or too green — add browns and turn.
• Dry and slow: add greens, water and turn.
• Small flies: bury food scraps in the centre instead of leaving them on top.
• Nothing happening in winter: normal — things slow down and pick up again in spring.

When it is ready to use

Depending on the season and how often you turn it, a heap will take six to twelve months to finish. It is ready when it looks dark, feels crumbly and smells earthy rather than rotten. A few eggshells or woody stems will survive — sift them out and drop them into the next batch.

Use it as a mulch around borders and shrubs, spread in a layer five to eight centimetres thick and kept clear of stems. Dig it into vegetable beds before planting, or mix one part compost with two parts multipurpose growing medium for containers and pots. A handful in the planting hole gives new shrubs a fine start.

Composting is one of those small garden habits that quietly improves everything else. Start with one bin, get the balance roughly right, and let the worms do the rest.