Every autumn I fetch leaves from the park to make leaf piles for frogs, beetles, and other garden wildlife. But this year I collected a few extra bags, to make leaf mould.

Relatively low in nutrients, leaf mould doesn’t feed the soil, but ‘boosts’ it, increasing soil-borne organisms and generating humus. There’s no need to dig it in – applied as a mulch, it’s taken deep into the soil by worms. The only snag is it takes two years to make.

There are various ways to make leaf mould. Unlike compost, which rots with the help of bacteria, leaves are mainly broken down by airborne fungus. This is a slower process, so they’re better off in a heap of their own. Some gardeners construct wire mesh cages and fill them with leaves, but you can also pop them in jute or plastic bags. the process can be accelerated by mowing and watering the leaves.

I don’t have space for a wire mesh cage, so I filled three jute bags with leaves and popped them in my shed. The park is mainly planted with London plane trees, but these produce waxy leaves which take years to break down. So I found a few small hazels, oaks and horse chestnuts to make my mould  (horse chestnut leaves are still quite waxy, but better than nothing). The best to use are oak, hornbeam and alder.

Although the leaves will take longer to break down, I didn’t water them because there were a few ladybirds among them, which I didn’t want to put at risk of fungal infections over winter (watering creates the fungal conditions that help break down leaves, but it can kill insects). Neither did I mow the leaves. I left the bags open slightly so any creatures caught up in the bags could escape. After half an hour, several more ladybirds had appeared.

It’s unlikely that debris blown onto a lawn would harbour hibernating insects, but if you retrieve leaves from under a hedge, or a sheltered corner of the garden, you could well be making beetle, caterpillar and ladybird mould too. Some gardeners even unwittingly pick up hibernating hedgehogs. These creatures make a great soil conditioner when dead, but most are more beneficial to the gardener alive.

There seem to be ladybirds everywhere at the moment, and I’m hoping the snug, dry conditions in my shed will make a nice hibernation spot for them. I just need to remember to leave the door open for them in spring.

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