Leaf Mould – How to Make and Use It

I’m forever raking up leaves at the moment. I shouldn’t moan. All those leaves present a golden opportunity to create leaf mould. And I blooming love the stuff!

Leaf mould is in essence rotted down leaves. Leaves contain up to 80% of the nutrients picked up by a tree. However, as they die, clever old trees reabsorb most of these nutrients. As a result, it doesn’t contain any nutritional value but that doesn’t matter as it’s wonderful in so many other ways.

Leaf Mould – Why I Love It

Leaf mould is a brilliant soil conditioner. Its lovely crumbly nature adds fantastic structure to your soil and provides a great home for earthworms and benefical bacteria.

Added to this, it is good at retaining water too. Apparently some studies have found that adding it increases water retention in soils by over 50%. That’s such a difference!

Although fallen leaves don’t have any nutritional value, they contain an important substance called lignin. Lignin prevents extreme mineral flows within the soil. Furthermore, clever old lignin can hold the soil’s nutrients in reserve. In other words while leaf mould may not bring new nutrition to the party, it’s brilliant at helping your soil hold onto the nutrients it has.

Leaf mould also smells absolutely wonderful – like a walk in a woodland. I love getting my hands in the stuff. And if, like me, you have trees, it’s free! It makes raking up all those leaves feel like a really worthwhile task.

How to Make Leaf Mould

Making leaf mould is not complicated, after all it is just composted leaves broken down by the slow cool action of fungi. This is unlike a compost heap where it’s warm, fast acting bacteria doing all the work.

That’s why with leaf mould you do need patience as it takes that slow acting fungi a little time. In fact it takes at least 6 months, and in my experience more like a year, to make leaf mould.

But while it may take a while to make, it involves no effort. There are two techniques.

Using a Cage

The fungi which break down the leaves operate best in airy damp conditions, which is why many people recommend using a special wooden or wire cage which you pile your leaves in to. To be worthwhile this needs to be 3 foot wide x 3 foot tall.

You simply pile the leaves up and dampen the whole thing and then leave it. Some suggest possibly checking the moisture levels from time to time and dampening the pile if it dries out. But to be honest with our UK weather, as long as the cage is open to the elements, our rain will probably keep it nice and moist for you.

Using a Bag

The second technique is easier still and is ideal if you don’t have the space for a fixed cage or can’t be bothered to make one. Simply put your leaves into a plastic sack. Old compost bags are perfect for this. I wouldn’t use black bin liners as I think they’re a bit too flimsy and in my experience become a mess. You can add some moisture but I find that the leaves I collect are generally already damp. I may add a bit of moisture to the leaves on the top.

The experts suggest you tie the bag, but I don’t as I want to pack as many leaves into my bags as possible. I think leaving the bag open to the elements further ensures my leaves stay damp. Then as the leaves rot a little I’ll push them down in the bag and then fold the top of the bag over.

It’s probably a good idea to have some holes in the bag lower down, to allow the air to circulate and spare water to drain as you want to avoid a slimy mess! You then simply leave it.

Again the experts suggest you check on the bags, turning the leaves a little periodically and making sure they haven’t dried out. I really don’t bother with this step. Instead, if I remember to do it, I pick the bags up and give them a bit of a shake.

Obviously old bags filled with leaves are a bit ugly so I stick all of mine out of sight, near our bins, and forget about them for a year.

I then tip the bags out after the year and use the lovely leaf mould as a mulch. Freeing up the bags to fill with leaves once again – it’s a wonderfully simple cycle!

If I want to use the leaf mould as a soil conditioner, the experts suggest leaving it a further year, but I’ve found mine is pretty good after 12 months. So I don’t hang about!

Additional Tips

Whichever technique you use, it’s worth running over the leaves a couple of times with your lawnmower before putting them in the cage/bag as smaller pieces decompose more quickly.

My neighbour Desi recommended I try this approach, and it’s great advice. It has the added bonus that if your mower has a bag, the leaves are collected up for you at the same time! Just rake your leaves into a bit of a pile and then mow. Put your mower on a high setting as you don’t want to cut your grass too. You will inevitably still collect up a few grass clippings but that’s not a problem, it can all go in your cage/bags; the grass clippings will rot down and will add some nutrient (nitrogen) to your leaf mould.

Don’t leave it until all the leaves have fallen before you start raking them up from your lawn. Leaving them may make it one big, convenient job but you may kill your grass in the process! Grass doesn’t like being left under a massive carpet of leaves for ages. So it’s much better to rake regularly.

Best Leaves for Leaf Mould

Despite having a relatively small garden, we’re lucky enough to have 15 mature, deciduous trees – no wonder I’m constantly raking! And I use all of the trees’ leaves for leaf mould. But if you want some tree specific top tips…

• Apparently the very best leaf mould is made from Oak and Hornbeam leaves, left to break down over two or more years. But I don’t have Hornbeam, Oak or patience! Thankfully, despite this, my leaf mould is superb!
• Trees with thicker leaves – Horse Chestnut, Sweet Chestnut, Sycamore – definitely need shredding first to give them a head start.
• Narrow leaves like Beech rot down quickly – I’ve definitely found this the case.
• Leaves from Evergreen trees (Holly, Laurel and Conifers) can take up to three years to compost down. Also, they produce an acidic leaf mould. So are best shredded first and then stored separately. Their leaf mould will be ideal for mulching your ericaceous plants, such as Camellias, Azaleas and Rhododendrons. (I love Camellias, here’s more about caring for them).
• Don’t remove the leaves from under hedges as these will provide cosy spots for creatures over-Wintering in your garden.
• Don’t ever take leaves from woodlands – those leaves are already being used by nature!
• I’ve also read that leaves raked up from roads should be avoided as they can be polluted.

7 Uses for Leaf Mould

Leaf mould, as already mentioned, is a brilliant soil improver. Simply dig it in to your beds or borders to improve structure. It’s particularly useful if your soil is heavy. You can sieve it first if you want, but I don’t bother.

If you’ve a bare bed of soil, putting a good old layer of leaf mould on it over Winter is a brilliant protector. It will prevent rains from washing away all of the soil’s nutrients.

I’m a massive mulching enthusiast. I mulch twice a year – in Autumn and Spring (you can read all about it here). In the Autumn I use my year-old leaf mould to mulch my flower beds, especially around my more tender plants. I feel the cosy layer keeps the plants snuggled up! Indeed, I’ve just used the leaf mould created using last year’s leaves, to mulch my north facing shaded bed.

You can of course also use leaf mould as a mulch at other times – for instance in the Summer to inhibit weeds and improve water retention.

If you’re big into lawn care (I’m really not sadly) you can mix sieved leaf mould with sharp sand and then brush it into the grass to top dress a lawn in Autumn. (The RHS provides lots of good advice here on lawn care if you’re interested.)

If unlike me, you’ve patience to develop your leaf mould over two years, sieved, two-year-old leaf mould, either on its own or mixed in equal parts with sharp sand, is good for seed sowing. That’s because seeds don’t need nutrients to germinate but they do want good soil structure.

I’ve also read that leaf mould, that’s two years old and sieved is pretty good compost for seedlings – add it to shop bought compost at a ratio of 25% leaf mould to 75% compost.

If you want to go one step further and create your own general potting compost, a mix of equal parts two-year-old leaf mould, sharp sand, garden compost and loam (soil to you and me!) is apparently gardening gold!

Leaf mould’s water retaining capabilities also make it a top choice to use in containers. I have a gazillion containers and watering them all is a major task. Adding several handfuls of year-old leaf mould to shop bought compost before planting up my containers definitely helps!

Conclusion

So that’s it, everything I know about leaf mould! But I guess my punch line is why not turn that raking chore into a positive thing. Create some leaf mould gold. You’ll feel so productive and your beds and borders will love you for it.