Make garden compost


Last updated March 2018

Composting is an easy way to save money, improve your garden and go green all at the same time. Read on to get the composting habit.

Why make garden compost?
Only a tiny garden? Use a wormery to compost waste.
Setting up a compost bin
Composting – the process
What to put on a compost heap
What to leave out of a compost heap
Dealing with pet poo waste

Why make garden compost?

Don’t throw away your garden or kitchen waste – use it to make free compost, or donate it someone else (we used to beg mowings from neighbours to heat up our compost heap).

Garden compost is useful for all types of garden, not just vegetable plots, because it:

  • Holds moisture in the soil. Garden compost will improve the water holding capacity of soils and help plants survive summer droughts. You don’t even have to dig the compost in if you don’t want to, just spread it over the soil and the worms will do the rest.
  • Prevents evaporation from soil. Used as a mulch around plants when the soil is moist, garden compost will prevent water evaporating from the soil’s surface too.
  • Assists drainage of very wet soil. Waterlogged or sticky soils are improved by garden compost, which assists drainage and improves the root zone for plants. The resultant thriving plants will take up water, thus further relieving the waterlogging.
  • Reduces peat use. Peat has been unnecessarily used by gardeners for soil improvement and mulching for years, which makes the return of garden composting even more important, helping to conserve peat stocks for more appropriate use.
  • Reduces waste. Composting is a great way to convert waste into something useful in an environmentally friendly way. You reduce the waste the local council has to deal with, reduce the demand for more landfill sites, save on fuel used to take waste to the tip, and produce a valuable garden product on site.
  • Saves your money – it’s free and no need to pay delivery charges or fuel to collect it
  • Saves your time/energy – no need to lug back bags of commercially produced stuff from the shops or garden centre.

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Only a tiny garden? Use a wormery to compost waste.

Those of you without a big garden are probably thinking, all very well, but where do I compost material and what do I do with the resulting compost? The answer is to use a worm compost bin, which is extremely effective at quickly reducing kitchen scraps to compost. Either buy a special wormery kit (eg from Greenfingers), or use any lidded container that holds about 15 litres and can be ventilated, plus worms (free from someone’s active compost heap, or bought from a fishing shop or online from Greenfingers). Note that worms for a wormery are NOT earthworms. The ones that live in our compost bin are very thin red worms.

If you don’t fancy worms, then try the Bokashi system (e.g.from Evengreener or Original Organics) that uses specially treated bran to help ferment your kitchen waste. They even do a wormery for dog and other pet poo which saves the problem of alternative disposal (see more on this below).

Use your resulting compost in window boxes and tubs, on flower borders, and around trees and shrubs, or give it to someone else who can use it, such as a friend, work colleague, or member of a local gardening club/allotment society (addresses in the library).

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Setting up a compost bin

Composting is really very easy. All you have to do is put a compost bin on a base of twiggy prunings or something similar (we use an old pallet) so that air can circulate, and then add anything organic as you accumulate it. Sooner or later, compost will be made, taking from 3 to 12 months depending on the type and quantity of materials added. Don’t worry about the lumpy appearance of the compost, because once spread over the soil or dug in, worms and other soil inhabitants complete the decomposition process.

There are neat compost bins and boxes on sale (see Greenfingers) on sale, but if you choose a design with an access flap at the base to remove the resulting compost, don’t expect this to be easy unless it is a very large flap. Only the perfectionist produces faultless compost; the rest of us end up with lumpy sticky stuff which cannot be extracted easily. Therefore look for a box or bin (or make one) that can be lifted off the heap or has a removable side to make access easy.

Rotating or tumbling compost bins are a good idea for keeping the contents mixed and airy, but be aware that in hard winters the contents cannot be turned if they are wet and have frozen into a solid lump.

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Composting – the process

A compost heap optimises conditions for decay and speeds up this natural process. Like a fire, it needs:

  • Air
  • Fuel
  • Heat (produced by microbial activity)

Air for composting

Heaps of lawn mowings turn into a slimy, smelly mess because after the first burst of heat, the mowings collapse and all the air spaces disappear. Although the decaying process continues, the end result is not pleasant to handle or smell, so dig a trench and bury it, where it can continue to rot without offence.

Avoid this situation by mixing tougher, drier materials with mowings, so that air spaces are maintained and decomposition can progress quickly. Also ensure that air can circulate within the heap, but not so much that all the heat is lost. Keep a lid on the heap too, because rain can waterlog the contents and reduce the air spaces.

The heap’s contents can be turned to provide more air, but few gardeners do this, unless they use a bin that can be tumbled or rotated. Rebuilding the heap at intervals also incorporates air and enables you to mix unrooted material from the edges with rotted material.

Fuel for composting

Anything that is derived from once-living matter is suitable fuel (see list in next section).

The bacteria that rot down the material need a nitrogen supply too, which can be provided by soft sappy material such as mowings or leaves of comfrey or nettle. Animal manures and urine also supply nitrogen, as do commercial compost makers or any cheap general/all-purpose fertiliser that has a high proportion of nitrogen (use sparingly after each 15cm (6 inch) thick layer).

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What to put on a compost heap

  • kitchen scraps
  • paper – torn up
  • papier mache trays (egg boxes etc)
  • wool
  • lawn mowings
  • weeds (with soil shaken off roots, without seedheads unless your heap gets up to 82 degrees C)
  • soft prunings
  • woody prunings (shredded).

Add garden waste to your compost heap immediately, but store kitchen waste in a lidded container until you have enough for your next trip to the bottom of the garden.
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What to leave out of a compost heap

  • meat and other scraps likely to attract animals, especially in winter when decay is slow. However you can put this waste in a wormery or Bokashi composter (return to top)
  • thorny material (because thorns stay sharp)
  • diseased material
  • weed seeds and seeding material (unless the heap reaches 82 degrees C)
  • roots of dandelion and bindweed, bulblets of celandine, rhizomes of couch grass, and the below-ground parts of any perennial plants that you don’t want to spread in your garden
  • leaves (instead put in separate wire netting enclosure or bag them up because leaf mould takes 2 years to form).
  • Poo, excrement, faeces… but see below

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Dealing with pet poo

Putting dog, cat and other animal waste into plastic bags and then into your dustbin is not the greenest way to deal with this material. You could bury it in the garden, but it will take time to rot down and eventually you run out of places to dig holes. So you could try composting, or using a Pet Poo Loo Wormery or a diy wormery container with a starter kit. However you compost it, for safety’s sake, you MUST NOT allow any of the final product anywhere near edible plants or children, as small composting systems are unlikely to get hot enough to destroy all dodgy organisms.
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