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The compost heap. In broad terms, a compost heap is a collection of green garden refuse — weeds, old pea and bean haulms, soft hedge trimmings, grass mowings, together with vegetable kitchen waste, leaves, straw and any other similar rubbish, such as shredded prunings and newspaper, which is piled so that it rots down by bacterial action. During the process, the part which is rotting becomes extremely warm; the warmer it gets, the better and quicker it rots down and in theory the amount of heat generated is enough to kill weed seeds present, though in practice this is not always the case. Rotting takes place quicker in summer than winter. Don’t use big pieces of woody waste as they will take too long, shred or cut them up finely first. Shred weeds with very tough roots finely so they rot.

You can compost a small amount of waste using one of the specially designed bins which can be purchased from garden companies and the like, but large amounts are best dealt with by making an enclosure of timber, or even small-mesh wire netting supported by posts, a minimum of 3 ft (900 mm) square, but 5 ft (1.5 m) is better, into which is piled layers of this soft, green garden rubbish until it forms a cube. Mix coarse rubbish with soft, wet material such as grass clippings so the waste rots quickly and sweetly. Grass clippings and suchlike settle into a soggy blanket which decomposes into a nasty smelly slime because the aerobic bacteria necessary for healthy compost-making cannot exist in such airless conditions, so unpleasant anaerobic ones get to work instead.

It is sometimes recommended that accelerators such as nitrogen-rich fertilizers, with or without lime or powdered chalk and beneficial bacteria to prevent the heap from becoming too acid during the rotting process, are added as each layer of refuse is placed on the heap, but I find that if the heap is properly constructed it will break down quite adequately without, and the soil acidity can be adjusted after the compost has been dug in if necessary.

It is also suggested that a very thin layer of soil can be spread over each 9 in. (225 mm) of garden refuse on the heap to introduce the bacteria to break down the waste, but if plants with roots have been added to the heap, there could be quite a lot of soil, and therefore bacteria, adhering to these, so I find this is not essential and can actually cool off the heap.

Cover the heap with perforated polythene, sacking, straw or similar when not being added to, to keep out excessive rainwater which would cool down the heap and make the compost soggy, and also to conserve warmth. Usable compost should be available in 6-9 months.

With a proprietary compost bin, you can speed up the rotting process by mixing up the last layer of material with the new waste being added. The already rotting rubbish gets the new refuse to start to rot so much quicker.

Well-made compost should be brown, sweet-smelling, moist but not soggy and look rather like a medium coarse peat. If it is a nasty, greenish-black, evil-smelling goo, it is generally because too much fine soft waste, like grass clippings, has been added at once, especially when steps haven’t been taken to exclude as much rainwater as possible.

It is a good idea, when you start composting, to have two heaps, bins, or whatever – one to keep adding to and one which is completed and left to finish rotting prior to digging in.

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