What is compost?

 Compost is a frequently used word and describes substances of vastly different qualities.

In my writing, I use the word to describe well rotted organic matter which is dark brown, reasonably crumbly and with few of the original ingredients being identifiable, as made over six months to a year in domestic gardens. I also use it to describe well rotted animal manure which fits the same description (in other words, not stable sweepings!).

Compost may also be the residue from growing mushrooms - 'mushroom compost' which is mainly straw and some peat - or from municipal treatment of garden refuse such as hedge prunings, grass mowings and weeds - 'green waste compost', which is best sieved to 15mm and even then often contains plenty of woody bits and of somewhat variable quality. Compost can also be made from leaves over at least a year.

The value of compost depends on both the original ingredients and on how they were composted. As a rule, animal manure has the most nutrients, but its lumpiness can make it more difficult to use. The nutrients are mostly stable after composting, so it can be spread in autumn and left on top of soil for the weather to finish breaking it down.

Compost is rarely worth sieving at home but purchased composts that have been sieved, or were so frequently turned that they are fine and crumbly, are delightfully easy to spread and can be used even on beds where carrots, parsnips and other difficult-to-germinate seeds are being sown.