What to Compost

Good compost comes down to a balance between two kinds of material: greens, which are wet and nitrogen-rich, and browns, which are dry and carbon-rich. Get the mix roughly right and almost any garden and kitchen waste will rot down sweetly.

Greens and browns

Greens are the wet, fresh, nitrogen-rich materials: vegetable and fruit scraps, fresh grass clippings, green prunings, coffee grounds and manure from chickens or other herbivores. Browns are the dry, carbon-rich materials: dry leaves, straw, shredded paper and cardboard, wood shavings and twigs. A rough balance of more browns than greens by volume keeps a heap aerated, sweet and rotting steadily.

• Greens: vege and fruit scraps, grass clippings, coffee grounds, herbivore manure
• Browns: dry leaves, straw, shredded paper and cardboard, twigs, wood shavings
• Also fine: tea leaves, crushed eggshells, spent plants, hair and natural fibres

What to leave out

Keep meat, fish, dairy and oily food out of an ordinary heap, since they rot foully and draw rats and flies. Leave out diseased plants and persistent weeds gone to seed unless your heap runs hot enough to kill them, and skip dog and cat waste, treated or painted timber, and anything synthetic. Glossy or heavily printed paper is best recycled rather than composted.

Getting the balance right

If a heap is wet, smelly or slimy, it has too many greens, so add browns and mix in air. If it is dry and nothing is happening, it has too many browns or too little moisture, so add greens and water. New Zealand grass clippings are the classic trap, since dumping a thick layer of fresh clippings turns to a stinking mat, so mix them through with browns instead. Keep the heap as damp as a wrung-out sponge and turning it occasionally speeds everything along.