How to make leafmould

Having collected up all the fallen leaves in your garden, it’s such a waste to simply throw them away. With the minimum of effort, you can turn them into a rich soil improver called leafmould or even sieve it to make home-made compost. Autumn leaves are nature’s way of recycling organic matter, forming a thick mulch on the forest floor that suppresses weeds and improves the soil. But in gardens autumn leaves need to be cleared-up to avoid problems. A layer of wet leaves on the lawn, for example, will smother and weaken the grass, making it vulnerable to disease infection during the winter months. Susceptible plants, such as alpines, will soon rot under a wet autumn blanket...and slippery leaves can be a hazard on paths and steps.

Tools for the job

Why collect autumn leaves?

• Keep the garden tidy
• Remove winter refuges for pests and diseases
• Stop leaves smothering and weakening lawns
• Prevent paths and steps becoming hazardous
• Avoid rotting alpines and other susceptible plants
• Make free soil improver

Clearing leaves

Autumn leaves are easier to collect when they are dry. Sweeping and raking can be backbreaking work especially if you have a large garden. So these days many opt for powered collectors, such as garden blowers and vacuums or hand-pushed leaf sweepers for clearing lawns and other flat surfaces. If you have a rotary mower, one trick that works well, is to set the cutting blade high and use the lawnmower to collect the leaves. Not only does this make life a lot easier, but you will shred the leaves in the process and mix in a sprinkling of sappy grass clippings too – both of which will help speed up the decomposition process.

Recycling autumn leaves Unlike a compost heap, a leafmould bin doesn’t heat up, so weed seeds and disease spores are not killed. For this reason, I always clear up diseased leaves from under fruit trees and roses and dispose of these separately by burning or binning – better to be safe than sorry with troublesome problems like apple and pear scab or rose blackspot. Since diseased leaves usually fall prematurely, they can be cleared before autumn leaf-fall proper gets underway. You can add all other types of autumn leaves to your leafmould bin. The operative word here is ‘autumn’, because you should not add evergreen leaves and conifer hedge trimmings since they will slow the rotting process – shred these and put them on the regular compost heap instead. The best leafmould is derived from oak and beech leaves. Both break down slowly into a lovely crumbly texture that’s a delight to handle.

Making a leafmould bin

If you have a lot of autumn leaves, you can make a simple metre-square leafmould enclosure out of four stout corner posts and a pen of rot-proof, fine-mesh netting. Site the bin somewhere out of the way and fill it with layers of leaves as they are collected, treading down the pile periodically to get more in. If the leaves are dry, water the heap before covering it with an old piece of carpet or similar to stop the leaves blowing about. With luck, you will have lots of lovely, crumbly leafmould to use when planting next autumn. But be patient, since it may take two or more years with rot-resistant leaves such as horse-chestnut. In a small garden where there are not enough leaves to fill a bin, it is still worth collecting them up in black polythene sacks. Again, add water if the leaves are dry, then tie up the sacks, puncture them a few times with a garden fork and place them somewhere out of sight, such as behind the shed. Small amounts of leaves may take longer to decompose, so inspect them after a year and replace the leaves if they require more ‘cooking’ time.

Quick leafmould You can increase the speed of leafmould decomposition by adding soft green lawn clippings. Mix the weed-free grass clippings into the leafmould bin or add a sprinkling to sacks of leaves as they are filled. Using this method, you can have useable leafmould in about half the time.

Home-made leafmould compost

Making compost out of well-rotted leafmould is straightforward, if a little laborious. All you need to do is to remove any lumps by putting it through a garden sieve. The sieved compost makes an excellent lawn top-dressing after spiking or scarifying in autumn, or can be used for potting up acid-loving plants, such as azaleas and rhododendrons.