How to compost Why compost

What is compost?

A tester filling up a compost bin

You can start composting at any time of year

Compost is an invaluable resource in the garden.

There are two types of compost that gardeners use:

Potting compost - sold in bags in garden centres, diy stores and supermarkets, this type of compost is used to raise plants from seeds and cuttings or for growing them in containers. 

Generally it is based on peat, but peat-free formulations are improving all the time as manufacturers try to reduce the amount of peat in their products.

Each year Which? trials the different brands available as performance varies greatly between the best and the worst.

Read our reviews and find the best compost for raising plants and best compost for container plants.

Garden compost - this is the compost that you can make yourself by recycling kitchen and garden waste. You'll need a compost bin or a wormery but otherwise it's simple to make. With a , you can have compost that's ready to use in as little as 14 weeks.

You can tell when compost is ready to use when it's brown in colour and has a crumbly texture. Depending on the technique used, this can take anything from a few months to a couple of years. Read our advice on different composting techniques. Either dig in the resulting brown, fibrous material or just spread it on the surface of the soil as a mulch where the worms will help break it down. Compost improves the soil by improving its ability to hold moisture and adding humus.

Discover our Best Buy compost bins, Best Buy wormeries and Best Buy tumbling compost bins.

What to compost

Composting is a good way of recycling both kitchen and garden waste.

 The following materials can all be used. As a rule of thumb, try to fill your compost bin with an equal volume of nitrogen-rich and carbon-rich material.

Nitrogen-rich (green) material includes:

  • Grass clippings – mix them in well with dry brown materials
  • Shrub prunings, shredded or finely chopped
  • Bedding and container plants after they’ve died off
  • Fresh farmyard manure
  • Raw vegetable remains
A tester adding grass to a pile to make compost

Adding similar amounts of green and brown waste is the key to making good compost

Carbon-rich (brown) material includes

  • Autumn leaves
  • Shredded paper
  • Straw and hay
  • Cardboard torn into small pieces
  • Flower stalks
  • Woody clippings

Do NOT add

  • Cooked food as it will attract rats
  • Perennial weeds and weeds in seed as they will survive the composting process and will be spread when the compost is used in the garden
  • Diseased plants as the disease may survive the composting process and could go on to affect other plants when the compost is used
  • Glossy paper as it won't rot down well and contains chemicals


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