Lots of leaves

Sunday, 25 May 2014

Pile of liquidambar leaves at the bottom of my garden

The incredibly (almost scarily) warm, dry weather we have experienced this month seems to have prolonged the display of autumn foliage everywhere this year. But the leaves are starting to fall, cloaking our gardens with a transient layer of colour - which I enjoy. However, there comes a time when they must be tidied up, and different gardeners have their own ideas on what is best to do with the leaves. I seem to have been haunted by fallen leaves this week, having spent a considerable amount of time raking them and sweeping them up. So I have had plenty of time to think about the value of deciduous leaves in the garden and how to deal with them.

It's hard to believe that once upon a time people used to burn autumn leaves to get rid of them! In our garden, all large deciduous leaves are raked into a pile, fed into a mulching machine then put onto one of our compost heaps, which also gets lawn clippings and mulched-up prunings of woody and semi-woody plants (and the occasional bag of manure). The pile is not turned (except by the resident brush turkeys!) so it does take quite a long time to break down. But when it has, the result is lovely dark compost like rich chocolate cake, which I use as a surface mulch or dig in when improving the soil before planting a new specimen. However, some people use the shredded leaves immediately as a mulch on flower beds, which is a good idea if you don't have a compost heap. One good tip I learned this week from a friend is to rake the leaves onto a large tarp then drag this to your compost heap or garden bed.

Liquidambar leaf

Shredding large leaves really does hasten decomposition: many of our leaves are from a large liquidambar tree (Liquidambar styraciflua), and they take much longer to break down if just piled up whole. Shredding also reduces the volume of the leaf pile as well. Another way to shred autumn leaves is to mow over them and add this material to the compost heap. Smaller leaves can simply be raked up and added to the compost heap or put around shrubs as a mulch, which I do with leaves from our crepe myrtle trees and Japanese maples.

Japanese maple in my driveway

A different idea is to place leaves in aerated plastic bags with a bit of blood and bone, and stow these away in the garage or garden shed. The leaves are supposed to break down into superb leaf mould, but I have to say that when I have tried this, all I had after a number of months was a bag of dry leaves. I think I did something wrong! However, the idea still has merit even if the leaf mould doesn't happen - these leaves can be shredded in summer and added to the compost heap when there is an abundance of 'green' (high nitrogen) material such as lawn clippings and soft prunings going into the heap, and little of the dry 'brown' (high carbon) material that is needed to form a well-balanced, actively decomposing heap.

If you don't have deciduous tree in your garden, there are a number of reasons for adding one: the beauty of colourful autumn leaves and the pretty carpet they make when they fall; the benefits of the leaves in enriching your garden soil once they have fallen from the tree and broken down; the extra sun that your garden will receive in winter when the tree is bare; and the excitement of seeing new buds in spring, opening up to perfect baby leaves that will go on to provide summer shade! For Sydney gardeners, refer to my previous blogs written in May 2009 and 2010 for some suggestions for suitable deciduous tree for our climate.