Autumn has a way of covering a garden faster than you can clear it.
One day the lawn is visible.
The next, it has disappeared beneath a russet carpet of beech, birch, maple and oak.
It is tempting to regard fallen leaves as another job on the list.
Rake them up. Bag them. Get rid of them.
But leaves are far too useful to waste.
Given time, they break down into leafmould: a dark, soft, crumbly material that is wonderfully useful for improving soil, mulching borders and helping compost retain moisture.
It is also one of the easiest things a gardener can make.
No complicated recipe.
No expensive equipment.
Just leaves, moisture and patience.
Nature has already worked out the rest.
What is leafmould?
Leafmould is the material produced when fallen leaves slowly decompose.
Unlike ordinary garden compost, which is made from a mixture of green and brown materials and relies heavily on bacterial activity, leafmould is created mainly through the slower action of fungi.
Think of the floor of a deciduous woodland.
Each autumn, another layer of leaves falls.
Over time those leaves soften, collapse and become part of the dark, moisture-retentive material beneath the trees.
Making leafmould in the garden simply borrows that natural process.
You gather the leaves into one place.
Keep them reasonably damp.
Then leave them alone.
There are few gardening techniques that reward neglect quite so generously.
Is leafmould a fertiliser?
Not really.
This is one of the most common misconceptions.
Leafmould contains some nutrients, but it is not particularly rich compared with well-made garden compost or manure.
Its greatest value lies elsewhere.
Leafmould is an excellent soil conditioner.
It can improve the structure of soil, help it retain moisture and create better conditions for roots and soil organisms.
On heavy soil, organic matter helps improve structure.
On lighter soil, it can help hold on to moisture.
Used as a mulch, leafmould also adds organic matter gradually as it continues breaking down.
So don’t think of it as feeding plants like a fertiliser.
Think of it as improving the place in which their roots have to live.
Much as we might improve a spare room before expecting anyone to move into it.
Why make leafmould?
Perhaps the best reason is that the raw material arrives free every autumn.
Trees have done the growing.
Wind has done much of the harvesting.
You merely need to collect the results.
Turning fallen leaves into leafmould has several advantages.
It keeps useful organic material in the garden rather than sending it away.
It provides a homemade mulch.
It improves soil structure.
It can help soil retain moisture.
And it reduces the need to buy as many bags of soil conditioner.
There is something satisfying about that.
A heap of leaves that looked like waste in November can become something genuinely useful a year or two later.
Gardening has always been good at changing the definition of rubbish.
How to make leafmould
There are several ways to do it, ranging from a purpose-built leaf bin to a simple bin bag.
The important ingredients are the same.
Leaves.
Air.
Moisture.
Time.
Step 1: Collect fallen leaves
Gather deciduous leaves from lawns, paths and borders.
Most common tree leaves will make useful leafmould.
Small, thin leaves generally break down faster than large, leathery ones.
Beech, hornbeam, birch and hazel leaves tend to rot down relatively readily.
Thicker leaves such as oak, plane and horse chestnut may take longer.
That is not a problem.
It simply requires patience.
Avoid collecting leaves that are obviously contaminated with litter, road salt or other pollutants.
And if you’re gathering leaves beyond your own garden, make sure you have permission to do so.
The local woodland floor already has its own residents and its own work to do.
Step 2: Shred the leaves if you want faster results
Whole leaves will eventually break down.
Chopped leaves usually break down faster.
One easy method is to run a lawnmower over dry fallen leaves before collecting them.
This chops them into smaller pieces and, if a little grass is mixed in, can help get decomposition moving.
You do not need to shred everything.
It is simply a useful shortcut if you have large or tough leaves and would rather not wait quite so long.
Step 3: Choose a leafmould bin
A leaf bin can be extremely simple.
Four posts with wire mesh wrapped around them will do the job perfectly well.
The mesh keeps the leaves contained while allowing air to move through.
Place the bin somewhere unobtrusive where it can remain for a long time without getting in the way.
A lightly shaded position is useful because it helps prevent the leaves drying out too quickly.
There is no need to tuck it into the darkest, wettest corner of the garden.
You are making leafmould.
Not creating a test of personal courage every time you visit it in January.
Step 4: Fill the bin
Pile in the leaves.
There is no need to build precise six-inch layers or alternate them with other garden material.
That is more relevant to traditional composting.
For leafmould, you can simply add leaves.
If they are very dry, water them as you go.
You want the pile to remain damp rather than saturated.
Think wrung-out sponge, not ornamental pond.
Then leave it.
Step 5: Keep the leaves moist
Moisture is important because dry leaves decompose very slowly.
Rain may do most of the work for you, especially in an open wire bin.
During prolonged dry weather, check the pile and add a little water if necessary.
There is generally no need to cover a wire leaf bin tightly with plastic.
A cover can help prevent excessive drying, but sealing the heap too thoroughly can reduce airflow.
Leafmould likes moisture and air.
It does not need central heating.
Can you make leafmould in bin bags?
Yes.
This is an excellent method if you have a small garden or only a modest quantity of leaves.
Fill strong plastic sacks with damp leaves.
Pierce several holes in the sides and bottom to allow air in and excess moisture out.
Tie the bags loosely and place them somewhere out of the way.
Then forget about them for a while.
This is especially useful if you don’t have room for a permanent leaf bin.
Label the bags with the year.
Otherwise, twelve months later, you’ll be standing behind the shed holding a mysterious black sack and trying to remember whether it contains leafmould, old plant pots or something you intended to take to the recycling centre.
How long does leafmould take?
This depends on the leaves, conditions and how fine you want the finished material to be.
After roughly a year, partly decomposed leafmould is often useful as a mulch.
Leave it for longer – commonly two years – and it becomes finer, darker and more crumbly.
Chopped leaves break down faster.
Tougher leaves take longer.
A dry pile will take longer still.
This is slow gardening.
There is no need to accelerate every process.
Put the leaves away one autumn and rediscover them another.
How do you know when leafmould is ready?
Finished leafmould bears little resemblance to the crisp leaves you collected.
It should be dark brown, soft and crumbly, with an earthy smell.
You may still find the occasional recognisable fragment.
That is perfectly normal.
If you’re using it as a mulch or soil conditioner, it does not need to look like sieved potting compost.
Gardens are remarkably tolerant of imperfection.
What can you use leafmould for?
Once you’ve made it, there are several very good places to use it.
Use leafmould as a mulch
Spread a layer over beds and borders.
This can help reduce moisture loss, protect the soil surface and gradually add organic matter.
Keep mulch away from the crowns and stems of plants rather than piling it directly against them.
Over time, worms and other soil organisms will help incorporate the material into the ground.
Which saves you some work.
Always an appealing arrangement.
Improve garden soil
Leafmould can be forked lightly into the upper layers of soil or simply spread on the surface and allowed to work its way in naturally.
Its real strength is improving texture and moisture management rather than delivering a large dose of nutrients.
On sandy soil, that extra moisture retention can be particularly useful.
On heavier ground, regular additions of organic matter can help create a more workable structure.
Use it around woodland plants
Plants that naturally grow beneath trees often appreciate conditions similar to those created by leaf litter.
Leafmould works particularly well around shade-loving and woodland-style plants because it mimics the sort of organic layer they encounter in nature.
Ferns, hostas, hellebores and many spring bulbs can all benefit from a mulch of well-rotted leaves.
There is something pleasingly circular about returning tree leaves to plants that are happiest beneath trees.
Add leafmould to homemade potting mixes
Well-rotted, fine leafmould can be useful as an ingredient in homemade growing media.
But it should not automatically be treated as a complete compost on its own.
Seedlings and container plants have specific needs for nutrients, drainage and consistency.
If you’re making your own compost mixes, use an established horticultural recipe suited to the plants you’re growing.
Leafmould can contribute structure and moisture retention.
It doesn’t have to do everything.
Use it as a lawn top dressing
Fine, well-rotted leafmould can be used sparingly on lawns.
A very thin layer can return organic matter to the soil without smothering the grass.
This is very different from tipping a wheelbarrow full onto one patch and hoping for the best.
Brush or rake a light dressing into the turf so the grass blades remain visible.
Subtlety is useful here.
Can diseased leaves go into leafmould?
This requires judgement.
Leaves affected by minor cosmetic problems do not necessarily need to be treated as hazardous waste.
However, where a tree or plant has a serious disease and guidance recommends removing and disposing of infected material, follow that advice rather than putting it into a home leafmould heap.
Home leafmould does not become hot enough to reliably destroy all plant pathogens.
If you’re uncertain about a particular disease, check species-specific guidance.
A little caution now can prevent a larger problem later.
What leaves should you avoid?
Most deciduous leaves are useful.
Evergreen leaves tend to be tougher and slower to break down.
Some can still be composted, but they may be better shredded and mixed with other materials rather than forming the bulk of a leafmould pile.
Avoid putting large amounts of pine needles into ordinary leafmould too.
They decompose slowly and are better handled separately or mixed in modest quantities.
There is no need to become overly selective, though.
Leafmould-making is forgiving.
The trees do not all need to submit matching paperwork.
Leave some leaves in the garden
One important point: don’t collect every leaf.
Fallen leaves are habitat.
Under hedges, beneath shrubs and in quiet corners, leaf litter provides shelter for insects and other invertebrates.
Birds forage through it.
Fungi break it down.
Small creatures overwinter beneath it.
So clear the lawn, paths and places where wet leaves cause problems, but consider leaving some elsewhere.
A good approach is to collect what you need and allow the rest to remain where it is useful.
This is one of the rare occasions when an incomplete autumn tidy-up can be both easier and better for wildlife.
Treasure it.
Leafmould versus garden compost
The two are useful for different reasons.
Garden compost is made from a mixture of materials such as vegetable peelings, grass clippings, plant trimmings and dry carbon-rich material. When well made, it contributes nutrients as well as organic matter.
Leafmould is made almost entirely from leaves and is particularly valuable for improving soil structure and moisture retention.
You do not need to choose between them.
Use both.
Compost for fertility.
Leafmould for structure.
The garden will happily accept the combination.
A free resource worth keeping
There is a tendency in autumn to think that the gardening year is ending.
In reality, the garden is simply changing how it works.
Leaves fall.
Fungi become busy.
Organic material returns to the soil.
What looks like an ending is already part of next year’s growth.
Making leafmould lets you join that cycle rather than interrupt it.
Collect the leaves.
Pile them somewhere damp.
Leave them alone.
Then, months later, dig into the heap and find that the garden has made something useful while you were busy doing other things.
Few gardening jobs offer such generous returns for so little intervention.
And the next time a windy October afternoon deposits half a tree across the lawn, perhaps don’t sigh quite so loudly.
You’re looking at next year’s soil conditioner.
Further Reading: My Garden Journal & Notes
