How to Make Leaf Mould and Use It in the Garden
Leaf mould is made from decomposed autumn leaves. Unlike ordinary compost, which is largely broken down by bacteria, leaf mould is produced mainly through the slower action of fungi.
The finished material is dark, crumbly and excellent for improving soil structure and moisture retention. It contains relatively few nutrients, but it is one of the most useful soil conditioners you can make—and the main ingredient is free.
Which leaves can you use?
Most deciduous tree leaves can be used, including:
Apple and pear
Maple
Beech
Birch
Hazel
Hornbeam
Cherry
Lime
Oak
Thin leaves usually break down more quickly than thick or waxy ones. Tough leaves can still be used, but shredding them will speed up the process.
Small quantities of evergreen leaves can be mixed in, but large amounts decompose very slowly. Avoid leaves collected from roads with heavy traffic or anywhere they may be contaminated with oil, litter or chemicals.
Collecting and preparing the leaves
Collect fallen leaves when they are damp, or moisten them after gathering. Dry leaves take much longer to begin decomposing.
Running a lawn mower over the leaves chops them into smaller pieces and greatly increases the surface area available to fungi. Shredding is helpful but not essential; whole leaves will still make leaf mould if given enough time.
There is no need to mix in kitchen scraps, grass clippings or manure. If these materials are added, the result becomes more like ordinary compost.
Making leaf mould in a simple container
A leaf-mould container needs to hold the leaves together while allowing some air to circulate. You can make one from wire mesh fixed around four posts, or use a ventilated compost bay.
Fill the container with damp leaves and compress them gently. They will settle considerably during the first few months, so add more when space becomes available.
An open top is usually suitable because rain helps keep the leaves damp. In a very wet climate, cover the container loosely if the contents become waterlogged.
Making leaf mould in bags
For a smaller quantity, place damp leaves into strong plastic sacks. Pierce several holes in the sides and base to allow air to enter and excess water to drain.
Tie the bags loosely and leave them in a shaded, out-of-the-way position. Check them occasionally and add a little water if the leaves have dried completely.
Reusable woven garden sacks also work and provide better airflow, although the leaves may dry more quickly.
Keeping the leaves moist
Leaf mould needs moisture, but the leaves should not sit in stagnant water. The material should feel damp throughout, similar to a wrung-out sponge.
During long, hot summers, check open containers occasionally. If the leaves are dry in the centre, add water slowly and mix or compress them again.
Turning is not essential. Mixing the leaves once or twice can help distribute moisture, but leaf mould can be made successfully with very little work.
How long does leaf mould take?
Shredded leaves may produce usable leaf mould within one year. Whole, thick leaves often need two years or longer to become fully crumbly.
After approximately one year, partly decomposed leaf mould may still contain recognisable pieces of leaf. This material is suitable for use as a surface mulch.
Well-rotted leaf mould is darker, finer and more uniform. It can be used as a soil conditioner or sieved for use in homemade potting mixtures.
The exact time depends on the type of leaf, moisture level, temperature and whether the leaves were shredded.
Using leaf mould as a mulch
Spread partly decomposed leaf mould around vegetables, fruit bushes, trees and perennial plants. It protects the soil surface, reduces evaporation and continues breaking down in place.
A layer around 2–5 cm deep is suitable in many situations. Keep it slightly away from vulnerable plant crowns and young stems.
Because leaf mould is relatively low in nutrients, it can be combined with compost when both soil conditioning and additional fertility are needed.
Using leaf mould to improve soil
Leaf mould helps sandy soil retain water and helps heavy soil develop a more open structure. Apply it to the surface and allow soil organisms to gradually incorporate it.
It is particularly useful where moisture retention is important, including around woodland plants, fruit bushes and perennial crops.
Leaf mould does not change one natural soil type into another. Its value lies in improving how the existing soil holds water, air and organic matter.
Using leaf mould in potting mixtures
Mature, well-decomposed leaf mould can replace part of the peat in homemade potting mixtures. Sieve it to remove twigs and pieces that have not fully broken down.
Leaf mould alone does not provide enough nutrients for most container plants. Combine it with mature compost and other suitable ingredients according to what you are growing.
For seed sowing, use only clean, fully decomposed material with a fine texture. Test a small quantity before relying on a homemade mixture for valuable seeds.
Common leaf-mould problems
If the leaves remain dry and unchanged, add water and compress them to improve contact between the materials.
A sour or stagnant smell usually means the leaves are waterlogged. Open the container or bag, loosen the contents and allow excess water to drain.
If decomposition is extremely slow, shred the leaves or simply allow more time. Thick oak and other tough leaves are valuable materials, but they naturally take longer to break down.
A valuable resource from the garden
Fallen leaves are not waste. Left beneath trees where practical, they protect the soil and return organic matter naturally. Leaves collected from paths, lawns and other areas can be turned into leaf mould with very little effort.
By storing them separately and allowing fungi time to work, you create a useful mulch and soil conditioner while keeping a valuable garden resource on your own land.
