With a nip in the air, storms approaching and the evenings becoming darker, it is clear that autumn has arrived.
This is a transitional time for lots of plants in the garden and some will already be unrecognisable from their summer peaks. One of the common autumn jobs is to clear leaves. But what should we do with them?
They can be left in some gardens or garden areas but in others it is best to clear them. At Thrive we love to use autumn leaves to create luxurious leaf mould compost, but there are other options too which we will explore.
It is best to collect leaves on calmer days so the wind doesn't blow away your efforts. Use a lawn rake on beds and lawned areas or a wide broom to sweep them into piles. Sometimes when the leaves collect between plants, we may need to use our hands or an onion hoe to make sure we don’t damage what is still living. One other consideration we should make in our gardens is how leaves left could support wildlife. Lots of smaller animals will use leaves as cover or even places to nest.
Before you begin clearing leaves have a look around your garden and notice how wind has naturally begun to transfer them across the space. They may collect against fencing and hedges or against larger shrubs. Another place they collect is in corners against buildings and sheds. Choose a couple of these places to put your leaves.
Particularly good places are against the plants, hedging and larger shrubs where a plethora of different wildlife congregates. Whether it's toads hibernating, solitary bees, moth and butterfly eggs or caterpillars.
You could even give these new homes some extra protection, with some porous fleece held in place with stone or logs.
You can bury leaves in smaller quantities using one bucket to one metre squared of bed without damaging nitrogen levels too much. Nitrogen is important for plant growth as it supports photosynthesis, and is used as a building block for all plant cells, giving way to flowering and fruiting. You can read more about sources of nitrogen and why it is important in our article on composting.
Whenever we place organic matter that hasn’t decomposed into soil, initially nitrogen is used up in the decomposing process which can leave the soil nitrogen deficient for some plants, particularly vegetables. In larger quantities it can be good to bury the leaves alongside decomposed material to add balance.
When digging over new beds getting them ready for planting up the following spring, this could also be a good way of working. If so, bury the leaves 2 spades depth down so that in the following couple of years as new plants establish themselves they will reach the buried leaf level. This will happen after they have decomposed and returned the nitrogen back into the soil. In general, it is best not to bury leaves in vegetable beds.
Herbs and leaves can also make a good mulch when applied direct to the bed. This is a good way of working with established beds and borders. Again, it is probably not so good for vegetable production as even on top of soil some initial loss of nitrogen takes place.
It is best to use shredded leaves. You can shred leaves by piling leaves onto a recently mown lawn and going over it with a mower, preferably one that collects as you go. On some mowers you can raise the cutting height and this would be another way to avoid perennial weed or seed getting into the leaf mulch.
Then spread the shredded leaves across beds and borders at around 6-15cm thick. Remember that some plants do not like moisture around their stems, trunks or crowns. A trick we use at Thrive is to place upturned pots over any crowns, which are trickier to avoid mulching over. Do this before you start and then remove any leaves from around any other plants that will be susceptible to disease and pest damage if they have constant moisture around them.
If shredding is going to be difficult then whole leaves can be used. Rather than forking them into the soil the following spring, you may have to remove them if they haven’t composted at all to avoid nitrogen loss.
A great way to use the astounding amounts of nutrients stored in leaves is to create leaf mould. Once created you will have an incredibly good textured nutrient-rich compost. This compost can be used like any other to support early plant growth. It is great as a general soil improver, mixing with other soil based composts to fill raised beds and containers. It can also be used within a mix of general gardening compost with some sand or perlite for drainage. This can then be used for seed sowing.
In smaller gardens and with less leaves you can create leaf mould in black bin bags. Bag up the leaves (preferably shredded) and create lots of small holes for aeration. If shredded, you will likely have a usable mould for general use in the following summer for seed sowing and other use.
The other way of creating leaf mould bins is similar to other compost bins. Keep the material in the bin and stop the wind blowing it away. Chicken wire around the structure will help. The easiest structure could be 4ft garden canes arranged in a circle or square with chicken wire secured around. You can wrap chicken wire around the first cane and then interweave it with the canes as you stake them down.
More permanent bins can be made with timber or reused pallets. Placing shredded leaves into the bins will speed up the decomposition. In larger quantities where you may have periods of dryness, it can take a bit longer to produce the luxurious texture and nutrient rich material that experienced gardeners have come to love.