While leaves can be composted, and green summer leaves usually are, but large quantities of leaves resulting from the autumn fall present a challenge calling for a different technique and are best converted to leafmould.
Even a cool compost bin will generate heat, in part, due to the activity of bacteria helping to breakdown its contents but the process of producing leafmould relies more on fungal action, than bacterial activity, and occurs at lower temperatures
so that while compost may take a few weeks or months depending on the type of leaves and process being used leafmould usually takes a year or two.
Most autumn leaves are an excellent source of carbon but depending on species may be slower to compost
than the rest of the material in the bin if using cold composting 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.
high in carbon, with a C/N ratio averaging at about 60 but ranging from 20-100 if they are to be composted they will need to be accompanied by a good source of nitrogen to maintain the C:N 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 tend to mat, this may result in some anaerobic decomposition. Some sources recommended collecting the leaves as soon as they
start falling, high and their cells are still hydrated while their nitrogen content is high making decomposition easier, but others wait for all the leaves to fall so that they only sweep up once.
Good leafmould 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, 8 pp)
- 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 peat substitute
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, in the 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, sieved and 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.