Making Leaf Mould for Free Soil Conditioner

Why Leaf Mould Deserves a Corner of Your Garden

Every autumn, Britain's streets, parks and gardens shed a fortune in free soil conditioner. Leaves that fall on your lawn, your path and your borders are not rubbish to be carted off — they are the raw material for leaf mould, one of the finest things you can dig into a border or spread across a seed bed. It is low in nutrients compared with compost, but that is precisely its charm: it improves soil structure, holds moisture, encourages earthworms and fungi, and helps heavy clay break down into something crumbly and workable.

Best of all, leaf mould asks almost nothing of you. No turning, no heat, no careful balance of greens and browns. Gather the leaves, keep them damp, leave them alone, and the fungi will do the work. A year or two later you have dark, friable material that costs nothing but a little patience and a few bin bags.

Which Leaves Make the Best Leaf Mould

Not all leaves rot at the same speed, and knowing the difference saves disappointment.

• Quick to break down (about a year): oak, beech, hornbeam, lime, ash, hazel and most fruit tree leaves. These are the ones to aim for if you want results sooner.
• Slow and leathery (up to two years or more): sycamore, horse chestnut, plane, walnut and sweet chestnut. Perfectly usable, just slower.
• Best shredded or mixed in: evergreen leaves such as holly, laurel and conifer needles. Conifer needles are acidic but make a decent mulch for rhododendrons, camellias and blueberries.
• Leave alone: anything from a diseased tree — rose black spot, for example — or leaves that have been treated with weedkiller. Bin those rather than composting them.

A mix of species is fine. In fact, mixing quick and slow leaves gives you a bin that starts working sooner and finishes steadily.

Bags, Bins and the Simple Wire Cage

There are two reliable methods, and both are wonderfully cheap.

The bin bag method suits small gardens and is almost foolproof. Use strong bags — the heavy-duty sort — and fill them with damp leaves. Punch a few drainage holes in the base and sides with a fork, tie the tops loosely so air can move, and stack them somewhere out of the way behind a shed or hedge. Check them every few months; if the contents feel dry, add a splash of water. If they are sodden, loosen the tie for a while.

The wire bin suits larger quantities. Make a cylinder about a metre across from wire mesh or chicken wire, held in place with a few sturdy stakes. Aim for a bin roughly a cubic metre in volume if you can, because a bigger mass holds moisture better and heats slightly in the middle. Fill it with leaves, tread them down gently as you go, and water the heap if autumn turns dry. A lid of old carpet or a sheet of polythene weighted with bricks keeps the rain from waterlogging it, but leave the sides open to the air.

Whichever you choose, site it on soil rather than concrete if possible. Worms and fungi will move in from below and speed everything up.

Keeping It Damp and Letting It Rot

Moisture is the single factor that decides whether you get leaf mould or a bag of dry, rattling leaves. The contents should feel like a wrung-out sponge — damp to the touch but not dripping. In a dry autumn, water the heap as you build it; in a wet winter, make sure water can drain away.

Speed things up by shredding leaves before they go in. Run the mower over them on the lawn with the collector attached, or stuff them into a bin and go at them briefly with a strimmer. Shredded leaves rot in roughly half the time and take up far less space.

Then wait. After twelve months, check the bags or the bottom of the bin. You are looking for a dark brown, crumbly material with a pleasant woodland smell, a bit like a cross between compost and old tea leaves.

• After one year: coarse and partly broken down — ideal as a mulch around shrubs and perennials.
• After two years: fine and friable — perfect for digging into borders, mixing into potting compost, or sieving over a seed bed as a nourishing top dressing.
• Still recognisably leaves? Give it another six months and check again.

Using Your Leaf Mould Around the Garden

Leaf mould is gentle enough to use almost anywhere. Spread a two to three inch layer over bare soil in autumn and let the worms pull it down. Fork it into vegetable beds to improve drainage on clay and water retention on sand. Sieve the finest material and mix it half and half with garden compost for sowing seeds, or use it as a mulch around raspberries, rhubarb and fruit bushes.

It also makes an excellent autumn top dressing for lawns, brushed in thinly to feed the soil beneath the turf. And a handful in the bottom of a planting hole gives new shrubs and trees a welcoming start.

One word of warning: do not spread fresh, unrotted leaves directly onto borders as a thick layer. They can mat down into a soggy blanket that sheds water and smothers small plants. Let them rot first — that is the whole point.

Start This Autumn, Thank Yourself Later

The beauty of leaf mould is that it turns a seasonal nuisance into a resource, and it costs you nothing but a few bags and a little patience. Sweep up what falls on your path and lawn, stuff it into a bin bag or a wire cage, keep it damp, and forget about it until next year. When you finally tip out that dark, crumbly treasure, you will wonder why you ever raked leaves into the green bin. Your soil — and the worms, beetles and fungi living in it — will thank you for years to come.