How to make leaf mould

Get outside and gather up as many leaves as you can to make leaf mould. It's really useful stuff in the garden, and you can't buy it anywhere, but it's really easy to make your own. Here's how I make mine:

I've spent lots of time this week raking up leaves in my clients' gardens. If there are still plenty lying on the ground where you are, then you still have time to make some lovely leaf mould.

Why make leaf mould?

"Leaf mould is always useful and you can never have too much" Monty Don, in his book "Down to Earth"

Leaf mould is an excellent soil conditioner. After all, in many situations in the wild, it is how the soil is conditioned naturally by the leaves on the ground beneath trees. 

For this reason, it is good practice to leave some fallen leaves on your borders to break down in situ and work back into the soil. 

There is certainly no need to remove every leaf. 

However, a covering of rotting leaves is not good for lawns, and may damage the crowns of perennials too if left to rot right on top of them. 

So it's worth removing leaves from these areas, as well as paths and areas where they will look particularly messy or be a slip hazard. Gathering them and allowing them to rot down under controlled conditions will give you leaf mould that you can use. 

Nobody seems to have found a commercially viable way of making leaf mould on a large scale so the only way you can get some is by  making your own.

Leaf mould can be used as a mulch for plants that grow in woodland type conditions, or added to heavy soil to help improve it. But it is probably best used by adding it to compost to make a really good mix for seedlings and young plants being potted on.  

How to make leaf mould

"Leaf mould is the easiest thing in the world to make" Monty Don

Making leaf mould is really simple and fairly quick to do, though you need somewhere to store it for at least a year before it's ready to use. But the process of collecting the leaves can take just a few minutes.

It's also very cheap, as the only materials you need are something to put the leaves in, which could be just a few plastic sacks.

But first you need some leaves:

A field full of leaves waiting to become leaf mould!

Just so you know, some leaves break down more quickly than others. This means that depending on which trees are dropping leaves where you're collecting them from, your leaf mould could be usable in a year or it could take longer.

You can help speed the process up by shredding your leaves, for example by running a lawn mower over them. Smaller pieces will decompose into leaf mould sooner.

I collect my leaves from the area just outside by back gate, and it's mostly beech, birch and willow. These leaves aren't too large and seem to just about break down to a usable leaf mould in 12 months. I just fill as many bags as I have room to store.

My new hessian bags full of leaves

This year, in an attempt to reduce plastic waste, I am using these hessian sacks. These are a natural, biodegradeable material which won't damage the environment after their useful life comes to an end.

I am also using plastic sacks as I have done in the past, to compare the results. My plastic sacks are made from recycled plastic, but this is not as eco-friendly as the hessian ones, since they will not biodegrade effectively and will end up having to go to landfill.

So I'm hoping for good results from the hessian sacks so that I can use these exclusively in future. Unlike the plastic bags they should last more than a year and can be used several times before they break down.

The other main method is to have a sort of cage, made of chicken wire, or as I've done on my allotment, an old compost bin. Leave the top open so that rain can get in, but perhaps have some wire on top to hold the leaves down and stop them blowing away.

My open top leaf bin - a recycled compost bin

All you have to do to make leaf mould is fill the bags (or your wire cage/compost bin) as full as you can (the final leaf mould will have shrunk down to a lesser volume so cram in as many as you can) and wet the leaves by watering them.

Water the leaves and keep them from drying out

Tie the tops of the bags, but not too tightly so there is open space at the top so that water can get in. Then put them somewhere out of the way. They aren't pretty to look at so I stash mine at the bottom of a garden where they can't usually be seen. That little piece of dead space behind your shed is probably perfect. 

My bags are stored at the bottom of the garden

The bags do need to be out in the open somewhere, not under cover. They need to be kept moist, so leaving them open to the elements helps. The hessian bags are a sort of mesh material so the water should soak through them easily enough. Making sure they don't dry out isn't difficult most of the year here in South Wales, but spraying them a bit using a watering can is all that is needed during dry periods. 

As leaf mould is created by the action of funghi, no heat is required, just moist conditions that encourage the funghi. This is different to compost which is created by the action of bacteria, and relies on heat to be effective. Compost heaps need to be a decent size to create more heat and work really well, and require a particular mix of different materials too. In contrast, even a small amount of leaves will break down easily. This is what makes it so much easier to make.

One year old leaf mould ready to open

After 12 months, you can see how last years leaf mould has shrunk down as the leaves have decomposed. You can open the bags up and check the final product. 

Leaf mould should be nice and fine and crumbly

If you've got nice crumbly and fairly fine leaf mould then it's worked! You can start using it in your garden, or mixing it with your compost for a really good potting mix. If it still has a lot of recognisable leaves or large pieces, you may want to store it for longer before using it.

I try and use mine after one year, as it takes less space than storing two or more years worth. Using small leaves and keeping them moist is the key. As I remove the bags and add it to my compost store, I can replace them with fresh bags of this years leaves, and the process goes on.

It really is that simple, so why not get out and make your own leaf mould this weekend?

Happy gardening,

Paul

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