Leaf mould, also known as leaf mulch, is a form of compost made entirely from tree leaves, usually deciduous trees. Those that shed their leaves every autumn.
As moist leaves decompose over time, they produce crumbly, earthy humus with a dark brown to black colour. It can be left to fall and decompose beneath the trees, such as a woodland or forest, or can be collected and decomposed elsewhere.
Leaf mould, surprisingly, does not contain much in the way of nutrients, and is therefore often used more as a mulch or to help with the structure of soil, or to retain moisture, or even to regulate soil temperature. Leaves contain up to 80% of the nutrients picked up by a tree. However, as they die, most of these nutrients are reabsorbed by the tree.
Raking and gathering leaves to make leaf mould is great physical exercise, building strength and burning calories. Nothing better on a crisp frosty morning!
One of the best parts of the autumn is that sweet, gentle aroma of leaves slowly decomposing. Not only is the intense heat of summer cooled off, but deciduous trees have dropped dead leaves onto the soil surface. We recommend that you do not mix evergreen leaves with deciduous ones. Keep pine needles in a separate pile as these take up to 3 yrs to rot down. Once rotted, they can be added to normal leaf mould.
It’s a wonder why so many people rake them up and give them to waste collection to be disposed of. Spreading and collecting leaves in the garden is such a powerful tool. The earth invented it! This is how lush forest floors practice regeneration on their own.
So why not mimic what nature has to show us? By using fallen leaves in our gardens, we help the soil retain moisture, and as they decompose, they help to structure to the soil below. The collection and use of leaf mould in the garden is also a super simple process.
Come the autumn, the leaves gently start to fall. Collect these and place them in a breathable container. This could be just a small box area of chicken wire mesh, or a self-contained bay. On a small scale use black bin bags, but don’t forget to put some holes in it for air & drainage. If you do use bin bags, shred the leaves first.
Tools of the trade are springbok rakes, brush, leaf blower/sucker, this also shreds, and of course the lawn mower for your grass areas.
Collect the leaves on a regular basis, possible weekly, and put the newly collected leaves on top of the previous ones, until the box or bay is full. If needs be, start another one. They will decompose from the bottom up if kept moist, which usually isn’t a problem in the British winter. Should the leaves be dry when collected, you could always run them through a shredder.
Leaves collected from a lawn with a mower, will automatically be shredded. This will quicken the decomposition. It will still take 2 years to break down but will be easier to sieve.
You will probably want more than just one bay. We tend to use 3 or 4 bays for collecting leaves from the garden each year. These are filled and left for one year without touching.
Leaf mould is slow to break down. It will generally take 2 years for leaf mould to decompose properly, before it’s ready for use. This is because it is broken down by the cool slow action of fungi. Garden compost as a comparison is no more than one year. This is broken down with quicker acting good bacteria.
The bays of collected leaves can be turned after one year. This is best done just before autumn. We find that the 3 bays will easily turn into one bay, as it has decomposed somewhat in that time. This then leaves 3 empty bays for collection of more leaves, and one bay that will be ready for use, this time next year.
Some leaves take a little longer to decay. Oak leaves take longer than say Birch. A good mix of different types of leaves is always beneficial.
After two years of decomposition, the leaf mould is ready for use.
It should have now turned into a brown, friable compost type material. Job done!
So now that I have this wonderful stuff, what do I do with it? Where and how can I best use this beautiful bounty to best use.
Firstly, let me will tell you how we use fully ready leaf mould.
For use in potting, the leaf mould is taken from the bay and sieved, through quite a large riddle, to get rid of any larger bits in the mix.
This then goes into a mix of 50% proprietary compost, and 25% leaf mould, & 25% home grown compost. This is what we use for potting Hostas.
The proprietary compost will have some trace elements and feed in it, as will the homemade compost. The leaf mould gives weight and structure to the compost in pots that Hostas just love.
The downside of using home-made compost or leaf mould is that you tend to get a lots of germinating seeds, mainly weeds, making the keeping the pots clean, more challenging. If you have the facilities, you could sterilise the mix before using. This should eradicate any seeds.
You could also combine the sieved compost with other elements such as compost or sand to produce an airy seed sowing mix, for those who wish to produce from seed. The sieve needs to be a little finer for seed sowing.
The main use, in most cases, is to either use it as a mulch, or to use it as a soil conditioner. This can be worked into the top 3” or 4 “ of the soil to improve it’s structure and ability to hold onto moisture.
My preference is not to use it as a mulch, because of the germinating weed seeds from it.
This is free garden goodness. The leaves drop and it costs nothing to clear and store for a little while. Of course you could always collect it from the forest floor, in black bin bags in the back of the car.
Leaf mould is a great additive, especially when it comes to building soil structure. It’s an abundant natural resource that is practically free, only requiring the expenditure of the energy it takes to collect it and break it down. When we say it holds moisture, we mean it. Leaf mould holds just as much moisture as peat moss. It’s not only beneficial for soil structure but has a linked benefit of attracting earthworms, who travel upward in the soil to consume and process decaying autumn leaves. You can spread it on garden beds or incorporate it into your soil as an annual soil refresher. Alternatively, let leaves do their own thing in your garden. You do not need to wait for 2 years to use leaf mould as a conditioner. You might be lucky and manage it in 18 months.
While the leaves sit there, they decompose and help your nearby plants or grass. They contain tons of beneficial bacteria, and they provide a habitat for overwintering insects of all kinds, especially your garden friends. Ground beetles, centipedes, millipedes, and spiders all help disintegrate the leaves. Pollinators like wasps, some bees, and moths make themselves a home in decaying leaves for winter. They emerge again in spring to do the work of pollinating your plants. What's not to like?
So! Let’s do it. Let’s collect some fallen leaves, put them somewhere out of the way, and get the benefits.
To learn more about Hostas, you may interested in reading : Grow and Maintain Hostas In Containers, Benefits of Companion Plants, What Are the Common Mistakes to Avoid When Growing Hostas?, Ways to Protect Your Hostas from Slugs and Snails and "Uncovering the Advantages of Bare Root Hostas:
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John Plant
Rewela Hostas
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