Why autumn leaves are a gift, not a chore

Every autumn, our gardens, parks and pavements are carpeted with fallen leaves. For many, it's a chore to be cleared and bagged for the council. But for wildlife gardeners, those leaves are free gold. Leaf mould is one of the finest soil conditioners you can make, and it costs nothing but patience. Unlike compost, which is broken down mainly by bacteria, leaf mould is the work of fungi. The result is a dark, crumbly, sweet-smelling material that improves soil structure, holds moisture and supports the teeming life beneath your feet.

Which leaves make the best leaf mould

Not all leaves are equal. The softer, thinner leaves break down quickest. Sycamore, ash, lime, and the leaves of fruit trees such as apple and pear can rot down in as little as a year. Oak, beech and hornbeam are slower, taking two years or more, but they produce particularly fine leaf mould. Evergreen leaves and conifer needles are acidic and waxy. They can take three years or more, so keep them separate. Pine and spruce needles make an excellent mulch for acid-loving plants like bilberry, heather and rhododendron, but don't add them to your main leaf mould heap unless you have space to wait.

If you have a mixture, don't worry. A blend of leaves will still rot down well, just at a variable pace. Avoid leaves from diseased trees, such as those with black spot on roses or horse chestnut leaf miner, as the fungus or pest may survive.

How to collect and store leaves

Collecting leaves is easy. A rake and a tarpaulin or a leaf blower will do. The best time is after a dry spell, when leaves are crisp. If they are wet, they will mat and rot anaerobically. You can store leaves in several ways.

• Wire cage: Make a cylinder from chicken wire, about a metre across, held in place with stakes. Fill with leaves and firm down. Good airflow.
• Bin bags: Fill bin bags with leaves, punch drainage holes in the sides, tie, and stack them in a corner. Add a sprinkle of water if leaves are dry. This is ideal for small gardens.
• Cardboard box: Line with a bin bag, fill with leaves, and keep moist. Not as good as wire, but works.
• Leaf mould bin: A plastic bin with the bottom cut out works well. Turn the leaves occasionally.

Whichever method you choose, keep the leaves damp but not soaked. If they dry out completely, decomposition stops. A handful of nitrogen-rich material, such as grass clippings or a little urine diluted in water, can speed things up. Don't add kitchen scraps or perennial weeds.

The waiting game: how long and what happens

Leaf mould is a slow craft. After one year, you'll have a coarse mulch. After two years, it becomes crumbly and dark. After three, it's a fine, almost peat-like material. The speed depends on leaf type, moisture and warmth. A wire cage in sun will work faster than a cold, shaded corner. You can speed things up by shredding leaves with a lawnmower before storing them, or by turning the heap every few months. Check after a year: if leaves are still recognisable, leave longer. If they crumble in your hand, they're ready.

Using leaf mould in a wildlife-friendly garden

Leaf mould is a superb soil conditioner. Use it as a mulch around native shrubs like hazel, hawthorn, dog rose and guelder rose. It suppresses weeds, retains moisture and feeds the soil. Spread a layer 5–10cm thick in autumn or spring, keeping it away from stems to avoid rotting. For woodland perennials such as wood anemone, wild garlic, primrose, bluebell and ferns, leaf mould mimics the rich leaf litter of a native woodland floor.

Sieved leaf mould is good for sowing seeds. Mix it with garden soil and sharp sand or grit to make a homemade potting compost. It holds moisture and nutrients without being too rich. Use it for potting on native plants, or as a top dressing for lawns and borders. You can also use it to improve heavy clay or light sandy soils.

Leaving some leaves for wildlife

As you gather leaves, remember that a tidy garden is not always a wildlife-friendly one. Fallen leaves are a vital habitat. Hedgehogs, frogs, toads, newts and slow worms shelter in leaf litter. Queen bumblebees burrow into it to hibernate. Moth and butterfly pupae overwinter among the leaves. Blackbirds, thrushes and robins forage through it for invertebrates. So leave a few piles in quiet corners, under hedges or behind shrubs. A leaf pile in a border is not mess; it's a refuge. A dedicated pile of leaves, twigs and logs will rot slowly and shelter wildlife for years.

By making leaf mould, you turn a waste product into a garden treasure. You feed your soil, support native plants and create homes for wildlife. It costs nothing but a little time. So this autumn, reach for the rake with a smile. Your garden will thank you, for years to come.