While leaves can be composted, and green summer leaves usually are, large quantities of leaves resulting from the autumn fall presents a challenge calling for a different technique.
Even a cool compost bin will generates heat, in part, due to the activity of bacteria breaking down its contents. The process of producing leafmould generally relies on fungal action rather than bacterial activity and occurs at lower temperatures
so that while compost takes a few weeks or months depending on the process being used leafmould usually takes a year or two.
The autumn leaves are an excellent source of carbon but are very slow to compost using conventional
techniques. However, as leafmould they become excellent mulch and a key ingredient when making homemade potting and seed composts (See more information on the following page Compost
Mixes ). Making your own potting mix is a personal contribution to saving peat bogs and reduces road miles by producing the product on site.
Leaves can take a long time to compost. They are “Browns”
being high in carbon, with a C/N ratio averaging at about 60 but ranging from 20-100. So if they are to be composted they will need to be accompanied by a good source of nitrogen to keep the balance in the bin. The amount of lignin, calcium and nitrogen
in the leaves will also affect the time it takes for them to breakdown. In general as leaves take a long time to compost and have a tendency to mat, this may result in anaerobic fermentation.
It has an earthy, dark
brown texture and the smell will remind you of a woodland floor in spring or early summer.
Leafmould can be used as :
- A mulch, it is very effective at retaining moisture being
able to hold up to 500 times its own weight, increased their water-holding capacity of the soil by almost 50 percent. (Hill, D.E. 1978. Leaf-mold for Soil Improvement in Home Gardens. Connecticut Agricultural Experiment Station Bulletin 774,
- A soil conditioner, reducing the soil density and making easier for roots to penetrate the and absorb nutrients,
- A potting mix or seed compost and as
- A renewable
It can be used after a year, when the leaves are beginning to break down and the material is easily crumbled, as a soil improver or mulch around shrubs, and in ther flower or vegetable garden. It
can also be used as a lawn top dressing in the Autumn.
However it is best kept for two years or more until it is dark brown in colour, crumbly with no real trace of original leaves visible.
At this stage it can be used to make a compost suitable for sowing seeds mixed with equal parts sharp sand and garden compost or to make a Potting compost using equal parts well rotted leafmould, sharp sand, loam and garden compost. See the
page on Homemade Seed and Potting compost for more information Compost Mixes
Some of the leaves can be bagged and saved for use as a source
of browns when composting during the winter when there is less garden waste available and the main addition to the compost bin is kitchen food waste.