After their final glorious show, the leaves are swirling down in their millions. They’ve been discarded by trees as they’re not needed for photosynthesis during winter dormancy. Though some nutrients have already been extracted by the parent tree the fallen leaves do improve soil structure by adding humus. So assuming it’s not raining too hard as you read this, you’ll find me busily scooping up as many as possible.
Like compost, I can never have enough leafmould because it’s the perfect mulch anywhere in the garden. Worms gradually improve structure by absorbing this humus into the soil. As a result, our plants can draw on a larger supply of water and nutrients. I also us leafmould to bulk up my home compost potting mixes.
How do leaves decompose and how do we collect and store them?
Although bacteria and soil invertebrates, like earthworms, woodlice, millipedes, mites and springtails, are important for breaking leaves down, fungi do most of the work. Bulky plant material contains complex lignocellulose that only fungi can process.
We often associate fungi with some of our foulest diseases, like potato blight, onion rot and canker, but the little known Kingdom of Fungi also includes the many species that break down plant lignocellulose. A few species specialise in the blades of leaves while others concentrate on stalks.
Some of these fungi may already be on our haul of leaves, but at the fruiting stage, fungi release countless spores that are blown from leaf to leaf, swelling the army of workers.
How you collect fallen leaves varies throughout the garden. It’s easy on the lawn. I use my rotary mower as a vacuum cleaner, setting the cutting blade quite high and chuntering to and fro. I find this works just as well on level paving.
The mower blade cuts up the leaves, leaving many more small edges for microorganisms to work on. This way you get fully rotted leafmould much more quickly. I find the whole process takes little more than 12 months.
A leaf blower can also chop up leaves, so works well on lawns and paving when leaves are dry. But because it readily vacuums up damaging little stones, it should be used very cautiously on pebbles. Safest to blow dry leaves off the pebbles onto grass or other solid surfaces. If that’s not possible, lay a sheet at one end of the path and use it as a collecting point.
Leave any that have fallen on a veg bed and let the worms get on with it. And provided flowers or bulbs aren’t being smothered by leaves, let them act as mulch. If you do need to remove some leaves, blow to a suitable collecting point.
‘Never’ is a word I rarely use except when talking about pernicious synthetic herbicides and pesticides, but I use it here. Never throw out your leaves. If you’ve a garden, you can use them.
If you don’t have space to make leafmould, either add to the compost bin, where leaves contribute valuable fibre to the mix. Or use collected leaves as mulch round shrubs, trees or even some perennials in a herbaceous border.
If you can make leafmould, the first golden rule is: keep leaves wet at all times as fungi and microbes need moisture to function.
With a medium-large garden and a good supply of leaves, why not build a dedicated pair of leafmould bays, filling each on alternate years. Construct a pair of metre square wooden or wire boxes, with slatted fronts for easy access.
If you’ve limited space, store leaves in large plastic bags. Pierce the base for drainage and always leave outside with the top open.
Plant of the week
Acer palmatum ‘Deshojo’ has slender-pointed leaves that turn brilliant shades of red and orange. The new spring foliage is vivid pink.
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