Paul Gargan
Green Fingers
“Fallen leaves lying on the grass in the November sun bring more happiness than the daffodils” – Cyril Connolly
If left on the grass of your lawn for long enough, leaves will cause it to weaken and yellow, which will encourage fungal diseases and bare patches. Gather them up and turn them into leafmould, which has many uses all around the garden.
Young leafmould – one to two years old – leaves that are beginning to break up and are easily crumbled in the hand can be used for mulch around shrubs, herbaceous perennials, trees and veg. Dig it in as a soil improver, Autumn top-dressing for lawns, or a winter cover for bare soil.
Well-rotted leafmould (two or more years old) can be used as above, and also mixed with equal parts sharp sand and garden compost as a seed-sowing mix or potting compost.
Leaves contain over 75% of the nutrients of the tree. Most are reabsorbed by the tree as the leaves die. What’s left is the fibre in the leaves’ cell structure, a substance called lignin. In your soil lignin acts as a buffer against extremes of mineral flows within the soil and can hold nutrients in reserve.
The only negative about leafmould is the time it takes to make. It contains mostly carbon, which takes longer to break down than the mostly nitrogen-rich materials you put into your compost heap. Leaves are broken down by the slow, cool action of fungi. If you put large amounts of leaves in your compost heap it will slow down the composting process, which is done by heat-generating bacteria. Unless you only have small amounts of leaves, don’t add them to your compost heap.
Large quantities of autumn leaves are best recycled separately in a leafmould heap or in smaller quantities in black plastic bags with holes punctured in them with a fork. The way to keep a heap in place is to drive posts into the ground, surround it with chicken wire or similar, and fill with leaves.
You can rake the leaves up or an easier way is to use your lawnmower with the grass-collection box on. This also chops the leaves up small, which will speed up the breaking-down process, and if you have grass clippings mixed in it will increase the nutrient content of your leafmould.
Make sure to soak the leaves as you are building up the layers, as they must be wet to break down. Check them every so often throughout the year, and wet them if they dry out. If they do dry out, mix them up as you wet them.
Oak, beech and hornbeam make the best leafmould; ash, sycamore and chestnut also work, but take longer to break down. Tough evergreen leaves like holly or laurel take too long and are best shredded and added to the compost heap.