Making Leaf Mould For Free Garden Compost

Why Leaf Mould Deserves A Place In Every Small Garden

Every autumn, pavements, parks and garden lawns across the UK disappear under a tide of leaves. Most of it gets bagged up by councils or raked into the green bin, but that debris is quietly one of the best soil improvers you can get your hands on — and it costs absolutely nothing. Leaf mould is what happens when fallen leaves are left to rot down slowly with the help of fungi rather than the hot, bacteria-driven process of a compost heap. The result is a dark, crumbly, sweet-smelling material that holds water like a sponge, conditions heavy clay and helps sandy soils cling onto moisture and nutrients.

For anyone gardening on a balcony, in a courtyard or on a small patch of lawn, leaf mould is especially appealing. It needs no turning, no activator and no expensive bin. A couple of wire hoops or a few old bin bags tucked behind the shed will do the job beautifully.

Which Leaves Are Worth Collecting

Not all leaves break down at the same speed, so it pays to know what you are gathering. Thin, soft leaves rot down quickest, often in a year or less, while thick, leathery or waxy leaves can take two or even three years.

• Quick to break down: oak, beech, hornbeam, lime, birch, cherry and most fruit tree leaves.
• Slow but worth it: sycamore, horse chestnut, walnut, sweet chestnut and plane.
• Best avoided: evergreen leaves such as holly, laurel and conifer needles. They are acidic and extremely slow, so keep them separate or leave them out altogether.

If you only have a small space, concentrate on gathering the softer leaves. A single black bin liner stuffed with oak or beech leaves will give you a bucket or two of lovely crumbly mould by the following autumn, which is plenty for top-dressing a few pots or working into a raised bed.

Making A Simple Wire Bin

The traditional method is a wire cage, and it is still the best for anyone with a bit of ground to spare. You need four sturdy stakes, ideally 90–120cm long, and a length of galvanised wire mesh with roughly 25mm holes. Hammer the stakes into the ground in a square about a metre apart, then wrap the mesh around the outside and secure it with garden wire or cable ties. Leave the top open and the base in contact with the soil so worms and microbes can move in freely.

Fill the bin with leaves as you collect them, giving them a gentle shake as they go in so they do not mat together. If the leaves are bone dry, water them as you build up the layers. Aim for a heap roughly a metre high — any smaller and it dries out too quickly; any bigger and the middle can turn sludgy. Leave it alone for a year, checking now and then that it has not dried to a crisp. A quick watering in a dry spell is all the maintenance it needs.

Bin Bag Method For Tiny Spaces

No room for a bin? The bin bag trick is perfect for flats, courtyards and balconies, and it is wonderfully undemanding. Use heavy-duty black refuse sacks, punch a few drainage holes in the bottom with a fork, then cram them full of damp leaves. Tie the tops loosely so air can still circulate, and stack them somewhere out of the way — behind a shed, under a bench, in a corner of the yard, or even on a balcony if you have a sturdy container to hide them in. Black bags warm up nicely in the sun, which speeds things along.

The secret is moisture. Leaves should feel like a wrung-out sponge. If they went in dry, add a mug of water before sealing. After twelve months, open a bag and check. If the contents are dark, crumbly and smell of woodland floor, it is ready. If not, give it a shake, add a splash of water if needed, reseal and leave it another six months.

Speeding Things Up And Knowing When It Is Ready

Patience is the main ingredient, but there are a few honest shortcuts. Chop leaves up by running a lawnmower over them on the grass, or give bags a good kick and shake every few months. Mixing in a handful of garden soil or finished compost introduces the fungi that do the work. Keeping the heap damp but never soggy matters far more than anything else.

Leaf mould comes in two useful grades. After a year you get a coarse, fibrous mulch ideal for spreading around shrubs, fruit bushes and perennials. After two years it turns into a fine, dark crumb you can sieve and use as seed-sowing compost mixed half and half with garden soil, or as a top dressing for containers.

Putting Your Leaf Mould To Work

However much you make, it will not go to waste. Fork coarse mould into the top few centimetres of borders to improve drainage on clay and boost water retention on sand. Spread a 5cm layer around roses, raspberries and soft fruit as a winter mulch, keeping it clear of stems. Dig fine mould into vegetable beds before planting, or use it as a potting mix ingredient for tomatoes and herbs. It also makes an excellent autumn top dressing for lawns, brushed thinly over the surface to feed the grass slowly.

Best of all, the whole process turns a chore you would otherwise be doing anyway — clearing the leaves — into a free, steady supply of the finest soil conditioner money cannot really buy. Start one bin or one bag this autumn, and by next year you will wonder why you ever threw the stuff away.