Composting basics
Kitchen peelings and dry leaves can become a dark, crumbly material that feeds your pots. A small bin with a lid is enough for a flat.
The four ingredients
The US Environmental Protection Agency (EPA) describes compost as the work of microorganisms that need four things:
- Browns (carbon): dry leaves, twigs and shredded plain paper or cardboard. Microorganisms use carbon as food.
- Greens (nitrogen): fruit and vegetable scraps and fresh green trimmings such as grass clippings. Nitrogen helps them grow and multiply.
- Water: the heap should feel like a wrung-out sponge.
- Air: turning the heap and adding browns let air in.
EPA suggests at least two to three times as much brown material as green, by volume, and covering fresh food scraps with a thick layer of browns.
Source: United States Environmental Protection Agency, checked 26 October 2026.
What to add and what to leave out
Add
- Fruit and vegetable scraps
- Dry leaves, plant stalks and twigs
- Coffee grounds, tea leaves in paper bags without staples
- Plain shredded paper and cardboard
- Crushed eggshells
Leave out
- Meat, fish, bones, dairy, fats and oils, which attract animals
- Diseased or pest-infested plants and weeds with seeds
- Pet waste and cat litter
- Glossy paper, treated or painted wood and produce stickers
EPA notes home heaps usually do not get hot enough to break down meat, dairy or “compostable” packaging, and suggests only small amounts of cooked food.
Source: United States Environmental Protection Agency, checked 26 October 2026.
Worm bins for small spaces
Worm composting (vermicomposting) can be done indoors. EPA’s guidance:
- Use red wigglers (Eisenia fetida), not worms dug from outdoors.
- Use a bin with a tight-fitting lid and a dark colour, drainage holes and a tray to catch liquid.
- Bed the worms in damp shredded paper, cardboard or dry leaves with a handful of soil.
- Feed chopped fruit and vegetable scraps, coffee grounds and crushed eggshells; avoid citrus, onion, garlic, meat, dairy and greasy food.
- Keep the bin at 59 to 77 °F (about 15 to 25 °C). Worms survive 32 to 95 °F (about 0 to 35 °C) if the bedding is at least 4 inches (10 cm) deep.
- Collect the castings from the bottom after three to six months.
Because EPA puts the worms’ upper survival limit around 35 °C, a bin left in a hot summer spot is at risk; keep it shaded or indoors during heat.
Source: United States Environmental Protection Agency; National Institute of Standards and Technology (NIST), checked 26 October 2026.
When is it ready?
EPA says compost is ready when the heap no longer heats up after mixing and you cannot see food scraps. Let it cure for at least four more weeks. Finished compost is dark, loose and crumbly and smells like fresh soil. A well-tended heap takes about three to five months; an untended one can take a year. Sieve out twigs, stones and stickers before use.
Fixing common problems
- Nothing is happening: it may be too dry. Add water and turn it.
- It smells bad: it may be too wet or short of air. Add browns and turn it.
Source: United States Environmental Protection Agency, checked 26 October 2026.
Using compost in pots
Compost improves water holding, but NC State suggests keeping it to 15 to 40 percent of a container mix because it often has a high pH. See the potting mix guide for recipes.
Source: NC State Extension, checked 26 October 2026.
General gardening information, not professional advice. Plant toxicity details are a starting point, not veterinary or medical advice: if a pet or child may have eaten a plant, contact a veterinarian or doctor promptly.