Green manures: love your soil this winter!

Green manures love your soil this winterBare soil suggests so much. It looks orderly and cared for, and says we're in control. But we're not. Nature loves to clothe bare ground in weeds because bare ground is vulnerable. Exposed soil is eroded by wind and rain, and with this comes leaching of its nutrients. If you love your soil, then cover it come winter. The best way is to sow green manures.

Green manures are plants such ryegrass, clovers, field beans, phacelia, mustards and buckwheat sown fairly thickly to produce a dense mat of green growth that is dug in (or cut down) before the plant flowers to increase soil fertility. Consider them the vegetarian alternative to farmyard manure. Like farmyard manure, they add organic matter to the soil via their leafy top growth. Organic matter is essential for growth: once broken down, it becomes humus (the soft black stuff in soil), which is essentially plant food. The more humus in the soil, the better aerated it is, thus water moves through it more easily, which improves plant growth.

Field beans, lupins and grazing ryes do the digging for you. Their extensive, deep roots will help break up soil. If you have a pan of clay, don't break your back trying to dig it apart – just sow some beans. You also get a lot more nitrogen in the soil, particularly with green manures from the pea family (clovers, field beans and vetches). And they weed on your behalf: green manures grow faster than weeds.

In autumn you can sow Hungarian grazing rye, crimson clover, vetches, field beans and buckwheat. Hungarian grazing rye locks nitrogen into the soil, has deep, extensive roots that break up clay soil and looks lovely in winter, a lush bed of green. It doesn't mind the snow and its only drawback is that you have to wait two weeks after digging in in spring before you can sow (a seed germination inhibitor is released as it breaks down). Field beans, vetches and crimson clover are especially good for thin, hungry soils.

Dig them in in spring, before they flower. Buckwheat is fast growing and stores phosphorus in its leaves. It has a deep root system and plenty of top growth, but will be smashed flat by the first frost. Leave it be, where it will act as mulch. Sow green manures into bare ground that has been watered. Scatter the seeds evenly by hand, gently rake into the soil, water again and walk away, safe in the knowledge that nature's doing the hard work for you.