How to Make Leafmould from Fallen Leaves

leaf mould

How to Make Leafmould from Fallen Leaves

Leafmould is an excellent way to use fallen leaves to add nutrients and structure to your soil. It can be used all year round as a soil conditioner or mulch to support a balance of nutrients in your garden, and is very easy to make. Leafmould is free compost!

Even in a small garden or a potted garden, leafmould is worth creating. Well-rotted quality leafmould is very good to use in pots, as it retains water for longer than standard compost. It does take a long time to rot down into fine matter but involves very little work on your part and the results can be rewarding.

Good quality compost and fertiliser can be expensive, putting many people off gardening or growing their own vegetables. With leafmould, you are creating your own compost, soil-conditioner fertiliser and mulch all at once! We’ve created this handy guide to help you prepare our favourite homemade garden hero. 

What Is Leafmould?

Leafmould is an organic mulch made simply from rotted leaves and garden clippings. It is easy to make and particularly good for conditioning dry soil and fertilising raspberry canes or other fruiting plants. Sometimes described as ‘Gardener’s Gold’, leafmould attracts worms, which rise up into the mulch and drag it deep into the soil, thus improving your chances of a high yield at harvest time. It is also good as a starter for new plants when mixed with potting compost.

leaf mould

When to make leafmould? 

It’s best to start your leafmould in the late autumn, after most leaves have fallen. This gives the leaves plenty of time to break down and decay before use. Leaves are almost entirely carbon, which means they take longer than grass clippings or food waste to rot. The full decaying process can take between six months and two years before the leaves are well rotted. 

Because the rotting time is so long, it doesn’t really matter when you start collecting leaves, as long as you recognise that they will flatten down and reduce as they decay, and you may need to keep adding more. If there are still leaves in your garden (as there are in mine) you can start making leaf mould now.

Types of leaves for leafmould 

You can use any leaves to make leafmould, as they will all eventually break down. That said, some are better than others, as evergreens take forever. By all accounts the best leaves to use for making leafmould are those that are smallest and thinnest, as these tend to rot the quickest. These are oak, ash, beech, hawthorn and hornbeam. Thick leaves like sycamore, chestnut, etc. are best shredded before being added to leafmould, and evergreens such as holly or laurel are best shredded and added to the compost heap. They will break down much more quickly amongst the food-waste than in a leaf pile. You can shred leaves easily by running them over with a lawn mower.

Choosing a Leafmould Method

What you use to make leafmould depends on what space you have available, and what resources. For larger gardens, you might want to fence off a metre-square next to your compost heap, with chicken-wire secured with posts or with pallets if you have any. Don’t attach the front side, instead allow it to be opened for easy access.

For those of us with less space, the humble black bin bag will suffice.

How To Make Leafmould 

  1. Collect as many leaves as you can, from your garden, park, quiet streets, or the edges of the allotment. It’s best to avoid leaves from next to main roads as they will be contaminated by air pollution and will bring these pollutants into your soil when you use it later.
  2. Fill your chosen container with the leaves. If you are using a large outdoor container to collect your leaves, simply rake or throw them in and you can leave them to rot down. 
  3. If you’ve opted for bin bags, fill each bag with leaves and add some water for moisture. Cut some slits or holes in the sides of the bag to allow air to move through them. 
  4. Leave them alone! Your open container will collect rain and keep the leaves moist. During dry periods, add a watering can full of water to replenish these damp conditions that are so conducive to rotting.
  5. Check your bags every month or so to ensure they are still moist. If the leaves feel dry, add some water.

You will be able to tell that your leafmould is ready when it has reduced to become a dark brown to black, earth-smelling fertiliser, resembling leafy wet compost.

Using Leafmould 

You can use your leafmould at any time of the year. If you have left your leafmould for six months to a year and are itching to reap the rewards, you can use it for an excellent mulch or soil-improver. Dig or turn it into beds, or spread it around on top or as mulch around the bases of shrubs, herbs, trees or vegetables and let the worms do the heavy lifting. In autumn, it works as a top dressing for lawns, reviving those luscious green grasses after summer’s heat. In winter, it makes an excellent covering for empty beds to keep the weeds at bay and condition the soil gradually. Because it has excellent water retention, leafmould is also fantastic in pots and containers. 

If you’ve got tons, you can leave your leafmould for another year. It will rot down even further into a high quality substance resembling compost that can be used to start seeds in the spring, or make your own free potting compost by mixing with equal parts sand, compost and soil.

Possible Leafmould Problems

 

Litter

When collecting leaves from parks and roadsides, be careful of litter that can get mixed in. You should sort carefully through your collection to avoid microplastics contaminating your leafmould.

Weeds

It is possible for open leaf-heaps to become infested with weeds, as they do not generate the same heat levels a compost heap does. Be careful when you start to use your leafmould. You should be able to pull out any weeds fairly easily as the leafmould will remain loose around the roots, but if it is truly infested don’t use it on beds where weeds would be unacceptable.

Tips For Speeding Up Leafmould

Before adding your leaves to your pile, shred them by running your lawnmower over them to make smaller pieces. These will rot much more quickly than whole leaves.

If your leafmould is taking forever to break down, turn it with a garden fork every month or so to spread the detritus-eating fungi around. When you are using a plastic bag, pick it up and give it a good shake. 

If you are using a leaf pile to make leafmould, cover it up with a large plastic tarpaulin or some bin bags to keep it warm and stop it from drying out.

leaf mould

Compost vs leafmould? 

Why not both? Compost and leafmould are very different substances on a chemical level and contribute to your garden in different ways. Compost, made from grass cuttings, garden waste and food scraps, is high in nutrients such as nitrogen, phosphorus and potassium. Leafmould, while it is fairly low in these famous garden nutrients, contains calcium and magnesium, along with traces of other nutrients. These are also important for plants, particularly shrubs, trees and other woody plants making it an excellent soil conditioner. 

In short, compost feeds your plants for high growth levels, while leafmould contributes to the soil structures and water retention of your beds and the overall health of your garden. 

Adding a few leaves to your compost heap can be good, as they will add a lot of dry matter. However, if you’re wondering why not to just throw the leaves into the compost and be done with it, you should know that leaves and compost rot in very different ways, with leaves being much slower to break down. Adding a lot of fallen leaves to your compost heap will simply result in leafy compost.

The Science Behind Leafmould

While compost is broken down by bacteria, resulting in quick decomposition and an awful smell, leafmould relies on fungal decay. It is thus much slower than compost to rot, as the fungi slowly consume the leaves by softening and eating them. This process occurs in cool, damp conditions, rather than the heat of a compost heap, which is why it doesn’t attract as many pests or flies, and why it doesn’t kill the seeds of weeds that get mixed in by accident. 

The fascinating thing about leafmould is that it contains a substance called lignin. This is the fibrous part of the leaf which forms its structure, the part which you see in the childhood pleasure of ‘skeleton leaves’, leaves that have almost completely rotted away to be just an outline and some fine threads. Lignin is a complex hydrocarbon which, used in leafmould as a mulch, enables the soil to retain a healthy nutrient balance more easily than soil with a lower concentration of plant matter.

leaf mould

Leafmould: Gardener’s Gold

Next time the leaves start to fall, get your binbags out and start collecting. With a very little effort on a cold afternoon, not to mention a fun garden activity for children, and you’ll be setting yourself up for excellent soil structures and nutrient balance for the next two years.

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