There’s something akin to alchemy in the making of leafmould – the idea that out of nature’s discards comes the most deliciously crumbly gardener’s gold. For those of you unfamiliar with leafmould it’s simply wondrous stuff. Earthy, dark brown and smelling like a woodland floor in spring, it’s what you get when leaves rot down over time. Leafmould can be used as a mulch, soil conditioner, potting mix or seed compost. It’s a benign fellow, low enough in nutrients so as not to scold tender seedlings but with just the right qualities to dramatically improve soil structure and boost its water retention.
If there’s one thing that isn’t in short supply in autumn, it’s fallen leaves! American gardeners have even named a season after this annual bounty. So it’s rakes, scoops and wheelbarrows at the ready as we prepare to collect some of this plenty and transform it into something special.
Leafmould Takes Time
Unlike a compost heap which generates heat and relies on bacteria to break down its contents, leafmould piles are a far more sedate affair. Fallen leaves are generally broken down by fungi, which slowly wend their way through a leaf’s structure, softening then digesting it for dinner. All this takes place in cool conditions, so that while compost takes a few months to reach maturity, leafmould usually takes a year – even two – before it’s ready to be put to good use about the garden.
This begs the question, why bother? Why not simply add the leaves to the compost bin? Certainly small quantities of leaves may be added to the composter but with so many leaves coming at once this arrangement is soon likely to become unstuck. Leafmould’s unique properties make it worth the very minimal effort that’s required to make it; all you are in essence doing is piling up the leaves into one place (in such a way that they don’t immediately blow away) then forgetting about them until the end result is ready to use. And that’s it.
Collecting Leaves for Leaf Mould
As well as collecting the leaves from your garden you could try sourcing leaves from public places. Avoid leaves from busy roadsides which are likely to be full of pollutants, some of them nasty and slow to dissipate – you don’t want these ending up on your vegetables beds!
While leaf blowers make short work of the job, unless you work for the local parks department or have a particularly large garden they may not be the most economical or practical solution. I’d always opt for my trusty spring tine rake. Half an hour spent raking does the job just as well and provides a free workout to boot. Always rake in the direction of any wind to avoid repeatedly going back over the same ground. If you’re collecting leaves from a lawn then consider using a rotary mower, which will shred the leaves and speed up the process while introducing a few grass clippings for additional nutrient content.
Not all leaves are equal. The holy trinity of fallen leaves are oak, beech and hornbeam. If you have one of these in the garden you’re in luck, as these three trees produce the best-quality leafmould. Other deciduous tree leaves also work well, though thicker leaves such as chestnut (horse and sweet), walnut and sycamore will take longer to break down. Tough, evergreen leaves like holly or laurel take too long for even the most patient gardener and are best shredded before adding to the compost heap. Pine tree needles can be collected to make an acidic leafmould suitable for ericaceous plants such as the blueberry.
Making the Leafmould
There are two options for making leafmould: the easy option and the even easier option. The easy option involves constructing a wire frame using chicken wire supported in the corners by sturdy posts. Bigger volumes of leaves work best, offering a buffer against weather conditions, so ensure your frame is at least a metre (3ft) wide and deep. Fix the chicken wire to the posts with galvanised fencing staples and position the whole setup in a sheltered corner of the garden. Periodically check your leafy investment, adding water if the leaves seem dry. A tarpaulin cover will help to keep the contents more consistently moist.
There are all sorts of leafmould accelerators on the market. Save your money and use what comes naturally – your pee. Urine can be applied directly by gentlemen members of the household (make sure the neighbours can’t see you!) or, more discretely, collected indoors before pouring over the pile. Fresh urine is sterile, safe, and it works wonders.
The even easier option for making leafmould is to simply scoop leaves up into bin bags. Fill the bags three-quarters full, tie them closed at the top then puncture holes into the bottom and sides to allow its contents to breathe. Place the bags out of the way and forget about them for a year or two.
Using Leafmould in the Garden
After one year most leafmould can be crumbled by hand and while it won’t be fully broken down, it’s good enough for the kitchen garden. Use it as a mulch around existing crops and fruit bushes, dig it in to improve the condition of your soil, or just leave it on the surface over winter for the earthworm population to dig it in for you.
Leafmould that’s a couple of years old will have a finer texture similar to the compost found in garden centres. By this stage it’s unlikely to show any traces of the original leaves. This beautiful, friable material can be used as above or as compost for seed sowing. Alternatively mix it with equal parts garden compost, sharp sand and good-quality garden soil to make your own (free!) potting compost.
By Benedict Vanheems. Photo credit-Leafmould bin: Far Closer, Rake with leaves: Wickenden