Although I’ve been making leaf mould for more than 25 years, the magic of the stuff gets me every time. At the beginning of the year, I put layers of semi-rotting leaves, planted potatoes, pumpkins and beans into the soil’s damp interiors, and now with the crops cleared away, I have a soil so soft and rich with worms it makes me want to strip naked and roll around in it. It’s some trip, leaf mould, it really is.
In essence, leaf mould is simple stuff. It is made from autumn leaves slowly decomposed by fungi until those papery leaves turn into a dark, soft, crumbly substance. The process is slow, and the reduction of vast piles of leaves results in only a few inches of end product that, although not nutrient rich – the trees mined that stuff back themselves in the process of leaf fall – is high in cellulose and lignin.
Somewhere in there is the magic, because this stuff is the most excellent soil conditioner. It retains water, while still maintaining a good structure, which makes it an excellent bed for seedling roots to take hold.
There are several ways to make leaf mould. The holy grail is made from oak or hornbeam, matured for two years. If you have the patience to do this, you will make the best seedling compost money can’t buy. Year-old leaf mould is pretty good, too – add it to shop-bought compost for new pots, up to 25% of the overall volume. Or top-dress existing pots with equal parts leaf mould to compost to make a mulch for spring.
Those fungi that do all the hard work breaking down the leaf structure do best in damp, airy conditions. Traditionally, this meant making a leaf mould cage out of chicken wire and allowing the autumn rains to do the work, but if you don’t have space for a cage, recycle old compost bags. These are ideal because they’re tough and won’t disintegrate, unlike bin liners, say. If you fold them inside out so they are black, they are slightly less of an eyesore. Punch extra holes into the bags with a fork to improve air flow, fill them up, tuck them into an out-of-sight corner and let the fungi do its magic.
Or take the lazy route, which is increasingly my preferred one. Gather up wet, semi-rotting leaves over the next few months (staying away from leaves on roads – they are often contaminated), spread them over the surface of bare soil and let the worms do the work. They will bury a good percentage to line their burrows. This turns out to be a perfect leaf mould-making place. And you, too, might just find yourself with soil you want to roll around in.