As you dispatch annual flowers and veg plants to the compost heap, you need to work out the best way to deal with the empty ground.

And because herbaceous borders are often close to trees and shrubs, any cleared spaces are often covered with fallen leaves. This also happens among perennial plantings.

The good news is that you needn't try to remove the leaves. Leaf litter improves the ground in lots of ways. By acting as a blanket, leaves help prevent nutrient loss during winter rain. They prevent heavy rain from compacting the soil, thereby damaging its structure. Pull back any mulch in the spring and you'll see what I mean. You'll find fine, crumbly ground, not the flat, hard surface of bare ground.

Leaf litter improves as well as protects the ground. Although leaves themselves add little or no nutrient to the garden, research has shown valuable nutrients are added during decomposition. Once leaves have been partly broken down by soil microbes, soil fauna such as mites, fly larvae and potworms get to work. (Potworms are the tiny white worms seen in compost bins. People often wrongly think they're baby compost or tiger worms.)

These soil creatures add goodness when digesting and excreting leaf material. Some years ago, the Nature Conservancy Council conducted trials in the Lake District. Scientists filled nylon mesh nets with oak and ash leaves and laid them on the ground. After six months they found the ash leaves had been stripped and many had been dragged into the soil by large earth worms. At the same time, springtails, mites and potworms worked away inside the nets.

The researchers conducted their trials in woodland areas and found that deciduous trees got 75 per cent of their nutrients from the previous year's leaf fall. They also discovered the process worked more quickly and efficiently in rich soil. So it's safe to say that a similar, if small-scale process could be happening in your garden.

If you can't enjoy this leaf harvest, it often pays to apply a protective biodegradable mulch - coir, bark or rough compost. But mulch also provides a safe haven for most garden pests, including slugs, cutworms and aphids. So, every few years after there's been a build-up of pests, dig carefully round the plants and leave the ground bare. This brings pests closer to the surface, and thrushes and robins will soon clean them up for you.

You can also keep the veg patch clean and healthy by using similar methods. As in the herbaceous border, you need to rotate your overwintering soil treatments.

Unfortunately the veg patch isn't usually blessed with a surfeit of leaves, so you need different kinds of mulch. I take delivery of a handy source of mulch every time I clean out a duck house, spreading the duck-enriched straw over my beds. Again, as with leaves, worms and tiny soil animals add their largesse to the ground. In the spring, I rake off and compost any remaining straw. You could use any other biodegradable material. As in the herbaceous border, mulches in the veg patch provide a safe haven for the baddies, too. So every two or three years, after the autumn dig, leave some ground bare and open for our avian friends.

Veg growers have one extra technique for soil management - sowing green manures, the classic organic tool. Different plant species - lupines, field beans, clovers, phacelia and grazing rye - are sown any time before mid September, after which germination rates are fairly poor. As the plants grow, they absorb nutrients and so prevent leaching. In spring, the goodness is returned to the soil when the plants are dug in. Even tender plants such as phacelia provide ground cover, so they too act as a mulch.