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Composting is an environmentally friendly way to give your plants the nutrients they need. This guide will show you how to create compost that will best serve your garden.

Over time, garden soil becomes depleted of the nutrients that plants need to grow. Many use feeds and fertilisers to overcome this issue, but alternatively you could improve the fertility and nutrient value of your soil by adding garden compost.

Composting is great for the environment as it reuses waste plant material on site and provides a free soil additive that increases the health and vitality of plants. Compost can be made very simply by anyone.

  • Improves soil fertility and structure
  • Makes use of waste plant material at your own site
  • Increases biodiversity in the garden
  • This is an enjoyable task that can be adjusted to suit the gardener's ability
  • Select a small ready-made composter, tumbler or wormery (a container where composting worms live, converting organic waste into compost)
  • Use a hedge cutter or lawn mower to cut up plant material into small pieces
  • Introduces children to the cycles of nature, decomposition and growth
  • Provides opportunities for bug hunting and searching for 'mini beasties'. Slow worms are commonly found in compost heaps (be careful when emptying the heap!)
  • Encourage them to help you when you are cutting and clearing or taking the lawn clippings to the compost area
  • Composter, space or you can dig a hole to put compost in
  • Compostable materials (see below)
  • Heat
  • Moisture
  • Time

1. Choose a site

Most gardens, unless they are very small, will benefit from having a compost heap. Although they are unlikely to attract flies and pests when filled correctly, you may want to choose a site that is not too close to your doors and windows. A site that is protected from extreme temperatures is ideal. It can be in full sun, light or full shade. In very small gardens it may be suitable to use a wormery as an alternative to break down kitchen and garden waste.

2. Decide on the type of compost bin or heap

The type of composter should suit your garden size, the types of plant material that it generates and your physical ability. If you have a large enough garden, then compost bins of at least 1m³ are recommended to enable aerobic breakdown to occur. You can buy composters made of wood or plastic, or you can make your own. Tumbling composters that make turning and mixing the compost easier are also available. Some local authorities encourage home composting by subsidising the cost of a new compost bin.

The Gardener's World website has advice on how to build a compost bin.

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3. Add composting material

Please see the lists below to see what should and shouldn't be added to your compost heap. Any pile of plant waste will eventually break down into ‘compost’ but there is a science behind creating good garden compost. There needs to be a balance between carbon rich plant material and nitrogen rich plant material. Carbon rich materials tend to be woody (e.g. twigs and nitrogen rich materials are soft end green eg grass clippings).

Scientists tend to agree on a ratio of about 25:1 carbon to nitrogen. In terms of making garden compost, this has been simplified to ‘brown’ material and ‘green’ material. One simplification of this is a rule of thumb, 6 inches of carbon rich material to 2 inches of nitrogen rich material.

Most gardens produce more nitrogen rich material in the summer months and more carbon rich material at other times, so getting the balance right may require advanced planning. Or you can mix whats available together anyway, but have to wait a little longer to get usable compost.

The smaller the pieces of plant material are, the quicker they will break down. Cutting up plant material using secateurs or similar can be time consuming, but a task that you may enjoy. Using a powered hedge cutter or running a rotary mower over a pile of materials will speed up this task. If you have lots of large woody waste, you could give hügelkultur a try.

If you have a large compost heap, it is probably easier to add the materials in alternating layers of carbon rich and nitrogen rich. If your compost bin is placed on a hard surface like concrete, it is best to add some garden soil to provide necessary microorganisms .

Once all your material is added you can cover it. This will prevent excess moisture and retain heat.

4. Compost ingredients to add

Nitrogen rich

  • Grass clippings and hay
  • Soft plant material such as annual weeds and old bedding plants
  • Raw vegetable and fruit waste from the kitchen
  • Coffee grounds and tea leaves
  • Comfrey leaves and nettles
  • Cut flowers and house plants

Carbon rich

  • Woody waste like prunings, hedge clippings, tomato haulms (stems) etc
  • Cardboard and paper
  • Wood ash

Don’t add

  • Animal waste
  • Meat, fish and bones
  • Cooked food
  • Coal ash
  • Dairy products

5. Turning your compost

This can be done every 2-4 weeks (or more frequently with a tumbler). Leaving your compost for at least 2 weeks allows heat to build up which aids the development of microorganisms, which break down the plant material.

Turning allows you to see how well the composting process is going. It also allows air to be incorporated into the mix. The outer edges of a compost bin tend to break down more slowly, so turning allows these bits to be moved into the middle. The compost may be too dry and if so you can add water.

This is then repeated until the compost is ready for use. If the compost seems to have stopped breaking down, you may choose to use an accelerator or activator to speed things up. These are nitrogen rich additives that will feed the microorganisms and include specially formulated commercial accelerators, seaweed, urine, nettles, comfrey and poultry manure.

If you have a large compost heap and the material to feed it, composting may take place aerobically and produce useable compost in a couple of months in summertime. Aerobic composting is decomposition of organic matter using microorganisms that require oxygen.

Most gardens however will have cooler heaps with mostly anaerobic breakdown occurring. You may have guessed that anaerobic composting is decomposition that occurs using microorganisms that don't require oxygen to survive. This can take months to over a year to produce useable compost. Compost is ready to use when it is dark, crumbly and smells a bit like garden soil, and not rotting vegetation.

6. Use your compost in the garden

Compost can be used around the garden as a mulch or soil conditioner. It can also be sieved and used as home made potting compost. Although the nutrient value of compost is relatively low when compared to animal manures or commercial fertilisers, the benefits it brings seem to outweigh this. This is partly due to the presence of microorganisms that appear to promote plant health and resilience, increasing resistance to pests and diseases. You can read more about this Planet Natural website.

Although compost heaps can get hot, the risk of fire is very low. However, it's worth knowing that turning compost heaps may release bioaerosols that may affect those with a chest condition.

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