Why kitchen waste deserves a spot in a small garden

Even a courtyard the size of a couple of paving slabs can produce genuinely good compost. The trick is to stop thinking about an open heap at the bottom of the garden and start thinking about a sealed system you can tuck beside a shed, a wheelie bin or a back door. A tumbler or a wormery deals with vegetable peelings, tea leaves, coffee grounds and dead houseplants quietly, without the smell, flies or rodent interest that put so many people off.

The payoff is worth it. Over a year, a typical household throws away a surprising weight of compostable material that could be going back into containers, hanging baskets and borders. Made at home, it saves you buying bags of peat-free multipurpose, and it gives you something better: a crumbly, dark, living material that holds moisture in pots and feeds the soil slowly.

Pick the right system: tumbler or wormery

Both suit small spaces, but they suit different households.

• A tumbler is a sealed drum on a stand. You fill one chamber, then rotate it every few days to aerate the contents. Dimensions are usually around a metre square, so it fits on a patio or path. It handles garden prunings as well as kitchen scraps, and it works reasonably well in winter, if a little slower. You harvest in batches — roughly two to four months for a full chamber in warm weather.
• A wormery is a stack of trays with a sump and a tap at the base. Brandling or tiger worms eat the waste and leave behind worm casts, which are superb for seed sowing and potting on. It takes up less room than a tumbler and handles cooked food better, but the worms are fussier: they dislike extremes of heat, cold and wet, and you will need to drain the liquid off every few weeks.

If your garden is tiny and mostly containers, a wormery is usually the better fit. If you generate a lot of prunings as well as peelings, choose a tumbler.

What to feed it (and what to keep out)

Variety is what makes good compost, but a few rules keep things sweet.

• Yes to: vegetable and fruit peelings, tea leaves and tea bags (tear them open if the bag is the plastic-welded sort), coffee grounds and filters, crushed eggshells, salad leaves past their best, and small quantities of cooked vegetable scraps in a tumbler.
• In moderation: citrus peel, onion skins and garlic, which are acidic and slow to break down. Chop them small and don't let them dominate. Grass clippings are fine in a tumbler, but add them thinly — a thick layer turns to slime.
• No: meat, fish, bones, dairy, oily foods or pet waste. These attract rats, foxes and flies, and a domestic system rarely gets hot enough to deal with them safely.

Chop everything roughly. A potato peeling the size of your thumb might sit there for weeks; the same peeling sliced into three will vanish.

Getting the mix right: greens, browns and moisture

Composting is mostly about balance. Kitchen scraps are "greens" — wet and nitrogen-rich. You need roughly two parts "browns" by volume to keep the mix open and absorbent. Keep a bag beside your bin so it is effortless:

• Shredded cardboard and egg boxes
• Toilet roll tubes, torn up
• Used kitchen roll (clean of grease)
• Paper bedding from a wormery, if you have one
• A handful of soil or finished compost now and then, to introduce microbes

The test is simple. Squeeze a handful: it should feel like a wrung-out sponge. Drier and nothing much happens; wetter and you get a sour, sludgy smell. Add browns and turn or rotate if it is too wet, and add a sprinkling of water if it is too dry.

Troubleshooting the common grumbles

Smell. Almost always too wet or too much green material. Add cardboard, mix thoroughly, and leave the lid off a tumbler for an hour or two on a dry day.

Fruit flies. Bury new scraps under the previous layer and stop adding fruit peel for a week. Keep the lid closed and wipe the rim.

Nothing is happening. Cold weather slows everything down; a tumbler in a shaded corner in January may sit quietly for weeks. Insulate it with a sack of leaves or an old blanket, and be patient.

Worms climbing the walls. The tray is too wet, too acidic or too warm. Add dry bedding, ease off citrus, and move the wormery into the shade or a shed.

From bin to border: using your finished compost

Tumbler compost is ready when it is dark, crumbly and smells of woodland floor rather than bin. If a few twigs or eggshells remain, sieve them out and return them to the next batch. Use it as a mulch around shrubs and perennials, fork it into beds, or mix it with bought compost for containers — around one part homemade to three parts multipurpose works well for most plants.

Worm casts are richer and best used more sparingly, as a top dressing or stirred into potting mix for tomatoes, herbs and seedlings. Dilute the liquid from the sump at roughly one part to ten parts water and use it as a fortnightly feed for hungry container plants. Nothing beats the small, satisfying loop of turning a bowl of tea leaves and carrot tops into something that makes your garden grow.