This is not your usual warm, fast-acting, bacteria-fuelled compost. Instead, fallen autumn leaves break down in a cool, fungi-fuelled environment.
Within six to 12 months, the young leaf mould can be used as a natural and attractive mulch for your garden. By this stage, the leaves have started to break down and collapse easily, and the mould is ideal for use around trees, shrubs and on garden beds, even pots, as it helps to keep down weeds and retain moisture.
Within a year or two the leaves will have completely broken down. The mould, by now a dark brown crumbly material, is not exactly brimful of nutrients (it can be low in nitrogen) but certainly has enough potassium, phosphate and other essential elements to make huge improvements to your soil’s structure and boost its water retention properties. When dug into the soil it will give your garden, and your benefactor trees especially, a welcome treat.
Contain your leaves
While you can simply rake your leaves into a pile in the corner of your garden and forget about them for a year or two, the mould is easier to manage if it’s contained.
For small gardens, a simple garbage bag is all it takes. After the leaves have been piled into the bag, soak them with water and tie up the opening. Make a depression at the top and punch a few holes there to let in the rain and more holes in the bottom to let out excess moisture. Then put the bag in a shady spot and forget about it until you need it.
For large gardens, make a very simple leaf bin by driving four stakes into the ground about a metre apart to make a square, then wrap with chicken wire. Pile in the leaves to 30cm to 45cm, then add a layer of nitrogen - either a handful of urea, ammonium nitrate, bone meal or grass clippings. This helps replace the nitrogen the leaves have lost as they die. Mix all this with some water to wet the leaves, but not saturate them. Repeat the layers.
If the pile is too big for the bin, cover with plastic or tarp and, as the leaves decompose, the level will drop.
Top tips for autumn leaf mould mulch
- Leaves left to rot on your lawn will kill it in the patches where they sit
- If leaves are left to lie around plants, they encourage snails and slugs
- Immature leaf mould used as mulch helps protect soils from white ants and cockroaches.
- Don’t use leaf mould on annuals or vegetables as these plants require the higher levels of nitrogen found in normal compost.
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