How to make compost for a healthy garden
What can I compost?
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
Urine (diluted with water 20:1)
Other green materials
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
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
Old bedding plants
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
Coal & coke ash
How do I make my compost?
You can make compost simply by adding compostable items to a compost heap when you feel like it. It will all compost eventually but may take a long time and if the mix is unbalanced, may not produce a very pleasant end product. With a little extra attention you could improve things dramatically. If you want to produce more compost in a short time, and are able to put more effort into it, follow the 'HOT HEAP' route.
An ideal mix
To make good compost you need a more or less equal amount of 'greens' and 'browns' by volume.
The heap route
Try, if possible, to collect enough compost materials to make a layer of at least 30cm or more in the compost bin. Weed the garden, mow the lawn, empty the kitchen bucket! Mix in some straw, woody prunings, scrunched up cardboard packaging eg cereal boxes this helps create air spaces within the heap. It may help if you place a few woody plant stems or small twigs on the bottom first as this will improve the air circulation and drainage.
Continue to fill the container as and when you have ingredients. If most of what you compost is kitchen waste, mix it with egg boxes, toilet roll middles and similar household paper and cardboard products to create a better balance.
When the container is full - which it may never be as the contents will sink as it composts - or when you decide to, stop adding any more. Then either just leave it to finish composting (which could take up to a year) or go to Step 4.
Remove the container from the material, or the material from the container whichever you find easiest. If the lower layers have composted, use this on the garden. Mix everything else together well. Add water if it is dry, or add dry material if it is soggy. Replace in the bin and leave to mature.
The heap route
Gather enough material to fill your compost container at one go. Some of this may have been stored in a cool heap and have started to rot slightly. Make sure you have a mixture of soft and tough materials.
Chop up tough items using shears, a sharp spade (lay items out on soil or grass to avoid jarring) or a shredder.
Mix ingredients together as much as possible before adding to the container. In particular, mix items, such as grass mowings and any shredded paper, which tend to settle and exclude air, with more open items that tend to dry out. Fill the container as above, watering as you go.
Give the heap a good mix
Within a few days, the heap is likely to get hot to the touch. When it begins to cool down, or a week or two later, turn the heap. Remove everything from the container or lift the container off and mix it all up, trying to get the outside to the inside. Add water if it is dry, or dry material if it is soggy. Replace in the bin.
The heap may well heat up again; the new supply of air you have mixed in allows the fast acting aerobic microbes, ie those that need oxygen, to continue with their work. Step 4 can be repeated several more times if you have the energy, but the heating will be less and less. When it no longer heats up again, leave it undisturbed to finish composting.
A hybrid route
Theres nothing wrong with doing a bit of both. Fill your heap as you create waste (as for the cool method), then turn it when you have time. This will help it heat up. You can turn it as much or as rarely as you please the more often you turn the heap, the quicker your compost will be ready.
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.
Compost hints & tips
These can be added to your compost heap but the best use of them is to make leafmould. Stuff wet leaves into black plastic sacks (loosely tied), or an open wire mesh container. The resulting leafmould is ready to use after a year or two.
Mix well with browns to avoid a slimy mess. Alternatively, leave on the lawn whenever possible - they will soon disappear and feed the grass; this will not cause 'thatch'. Can also be mixed into a leafmould heap, or used directly as a soil mulch.
Plant materials suffering from soil-borne diseases such as clubroot and white rot should not be added to a compost heap. Anything else can be safely composted in a hot heap. Diseases that dont need living matter to survive, such as grey mould, mildews, and wilts, may survive in a cold heap. But heat is not the only factor that will kill diseases: the intense microbial activity in a compost heap also helps to dispose of them. Some diseases, such as tomato and potato blight need living plant tissue to survive and will not last long without it. It is fine to add foliage suffering from these diseases to your hot or cold compost heap.
If in doubt, leave it out. Problem materials can be sent to your local council green waste recycling facility where the composting methods are hot enough to kill any problem organisms.
Some perennial weeds will be killed in a hot heap; avoid really persistent horrors such as celandine, docks, bulbous buttercup, ground elder and bindweed. Don't burn or dump these weeds - they are rich in plant foods. Mix with grass mowings in a plastic sack. Tie it up and leave for a few months until the weeds are no longer recognisable, then add to the compost heap. Or send them to your local council green waste recycling facility where the composting methods are hot enough to kill them off.
Weed seeds may survive a cool heap, but should be killed in a hot one. If your finished compost tends to grow weeds, dig it in rather than spreading it on the soil surface.
Hedge clippings and prunings
Chop or shred tough prunings and clippings from evergreen hedges before adding to a mixed compost heap. Compost large quantities separately; even unshredded they will compost eventually. Mix with grass or other activating material; water well. Tread down the heap, then cover. In anything from a few months to a few years you will have a coarse mulch which can be used on perennial beds.
Strawy horse and cattle manure composts well. Manure mixed with wood shavings should be left to rot until the shavings have decomposed. If it is dry, water well and mix with grass mowings, poultry manure or other activating (ie green or nitrogen rich) material. When rotted use as a surface mulch.
Small pets, like hamsters, don't produce many droppings but you can still use their waste as a strawy addition to the compost heap. Guinea pigs are marvellous - they love eating weeds and convert them quickly to prime compost material!
Newspaper can be added to a compost heap, but in any quantity it should go for recycling into more paper. Cardboard, paper towels and other paper items can be scrunched up and composted. They are particularly useful where kitchen scraps make up a high proportion of the compost ingredients. Glossy paper takes a long time to rot down. Coloured inks are quite safe to compost.
Sawdust and wood shavings
Very slow to decay. Raw or uncomposted wood shavings incorporated into the soil can lock up soil nitrogen, making it unavailable for plants for a year or more. Add in small quantities; balance with quick-to-rot activating materials. See also 'Animal manures' above. Do not use if treated with wood preservatives.
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.
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