How to make compost
Making and using compost is the cornerstone of organic gardening - if you want to 'Grow Your Own', there's no better place to start.
The finished product is rich, dark, crumbly and sweet-smelling. It is made of recycled garden and kitchen waste, and can also include paper products. It is used to feed and condition the soil and in making potting mixes. Around 40 per cent of the average dustbin contents are suitable for home-composting so it helps cut down on landfill too.
Making compost is often considered to be complex but all you need to do is provide the right ingredients and let nature do the rest however, a little know-how will help you make better compost, more efficiently.
Where do I make my compost?
There are a variety of bins on the market but they are all just a container for the composting process. A bin is not strictly necessary you can just build a heap and cover it over with some polythene or cardboard. However, bins do look neater and are easier to manage. You can build your own, buy one from any number of suppliers, including The Organic Gardening Catalogue, or get one cheaply from your local council contact the Waste and Recycling Department at your local council for more information or visit the recycle now website: www.recyclenow.com
The ideal compost bin is:
- easily accessible
- has no gaps in the sides and may be insulated with cardboard or straw
- has a lid or cover
And is located:
- in a sunny or semi-shaded position
- directly on the soil or turf
- away from water-courses
- Anything that was once living will compost, but some items are best avoided. Meat, dairy and cooked food can attract vermin and should not be home-composted.
- For best results, use a mixture of types of ingredient. The right balance is something learnt by experience, but a rough guide is to use equal amounts by volume of greens and browns (see below).
- Some things, like grass mowings and soft young weeds, rot quickly. They work as 'activators', getting the composting started, but on their own will decay to a smelly mess.
- Older and tougher plant material is slower to rot but gives body to the finished compost - and usually makes up the bulk of a compost heap. Woody items decay very slowly; they are best chopped or shredded first, where appropriate.
'Greens' or nitrogen rich ingredients
- Grass Cuttittings
- Raw vegetable peelings from your kitchen
- Tea bags and leaves, coffee grounds
- Young green weed growth avoid weeds with seeds
- Soft green prunings
- Animal manure from herbivores eg cows and horses
- Poultry manure and bedding
'Browns' or carbon rich ingredients - slow to rot
- Cardboard eg. cereal packets and egg boxes
- Waste paper and junk mail, including shredded confidential waste
- Cardboard tubes
- Glossy magazines although it is better for the environment to pass them on to your local doctors or dentists' surgery or send them for recycling
- Newspaper, although it is better for the environment to send your newspapers for recycling
- Bedding from vegetarian pets eg rabbits, guinea pigs, hay, straw, shredded paper, wood shavings
- Tough hedge clippings
- Woody prunings
- Old bedding plants
- Wood shavings
- Fallen leaves can be composted but the best use of them is to make leafmould
Other compostable items
- Wood ash, in moderation
- Hair, nail clippings
- Egg shells (crushed)
- Natural fibres eg. 100% wool or cotton
Do NOT compost
- Cooked food
- Coal & coke ash
- Cat litter
- Dog faeces
- Disposable diapers
When is it ready?
Compost can be made in as little as six to eight weeks, or, more usually, it can take a year or more. In general, the more effort you put in, the quicker you will get compost.
When the ingredients you have put in your container have turned into a dark brown, earthy smelling material, the composting process is complete. It is then best left for a month or two to 'mature' before it is used. Don't worry if your compost is not fine and crumbly. Even if it is lumpy, sticky or stringy, with bits of twig and eggshell still obvious, it is quite usable. It can be sieved before using if you prefer. Any large bits can be added back into your new compost heap.
Composting questions answered
Is garden compost the same as bagged 'multipurpose' compost?
No. Sowing, potting and multipurpose composts that you buy in garden centres are mixtures of various materials such as shredded bark, sand, coir and fertilisers. These are used for raising seedlings and growing plants in pots.
Will a compost heap breed pests?
Compost is made by a host of small and microscopic creatures. These are not pests and will not overrun your garden. Slugs are often found in compost heaps, some species feed on decaying organic matter and are a valuable part of the composting process.
Do I need any special equipment?
A garden fork is the only essential item for turning and spreading compost. A compost bin keeps everything neater but it is not essential.
Will a compost heap attract rats?
Rats may visit a compost heap if they are already present in the area but composting does not generally attract the rats in the first place. If rats or mice are nesting in your compost heap, this is a sign that the heap is too dry. Add water until it has the consistency of a wrung-out sponge. For more information, see our factsheet GG1 Rats and the gardener.
Is compost safe to handle?
Yes, if the usual garden hygiene rules are followed. Keep cuts covered, wash hands before eating and keep your anti-tetanus protection up to date.
Does a compost heap have to get hot?
No. A medium-sized compost heap can heat up to 60C in a few days. The heat helps to make quicker compost, and to kill weeds and diseases. But your compost may never heat up, especially if it is made over a long period. The compost can be just as good, but it will take longer to be ready for use.
Does compost spread weeds and diseases?
Some weed seeds and plant diseases will survive in a slow, cool compost heap - if you add them in the first place.
Do I need a shredder to make compost?
No. A shredder can be very useful where there is a lot of woody material to be composted, but it is not essential.
Can I compost poisonous plants?
Yes. The toxins from rhubarb, yew, laurel and other poisonous plants are all broken down during the composting process and will not cause any damage to you or your garden.
Ants are nesting in my compost heap. Help!
Ants do have some small part to play in the composting process but the presence of nests in the heap is a sign that it is too dry. Water it thoroughly, or, if some parts are wetter than others, give it a good mix or turn.
Every time I open my bin I am assailed by masses of tiny 'fruit flies' why is this?
These are part of the decomposition process but their numbers can be reduced by burying any fruit waste among other ingredients. Flies are also a sign that the compost is a little too wet or has too many 'green' ingredients. Make sure that the bin has a lid and add 'brown' ingredients such as straw, cardboard or paper to re-balance the heap. Mix it in well.
There's a wasps nest in my bin what shall I do?
There is no 'organic' way to get rid of wasps. However, they do not return to the same nest every year so the problem will be over when autumn comes. If you can, leave the wasps alone as they are useful predators for garden pests. If they cannot be left (in a school garden, for example) then call your local council's Environmental Health Department for advice. To avoid the problem in future, make sure that your heap does not get too dry, make sure it has a lid and that the sides are solid, with no air gaps.