How to Make and Use Leaf Mold

How to Make and Use Leaf Mulch
Photo: © Marie Iannotti

They’re free. You’re going to rake them up anyway. Why not turn your leaves into something your garden will love your for?

What is Leaf Mold?

Simply put, leaf mold is fully decomposed leaves. Don’t turn up your nose. Leaf mold has a rich, earthy scent and a dark, crumbly texture that could make regular compost jealous.

How Do You Make Leaf Compost?

It couldn’t be easier. Just rake your leaves into a pile and let them rot.

The more compact the pile, the faster they will decompose. One year I had stored some leaves in those tall, brown paper, recycling bags, to use as brown material in my compost. I never got around to using them and by spring, not only had the bag disintegrated, the leaf had turned into the best compost I’ve ever made.

The leaf mold making process is very similar to making traditional compost - but easier. You can simply pile your leaves and leave them to rot or you can contain them in a wire bin or any other composting contraption. Moisten them and toss a tarp or some other cover over the pile, to maintain the moisture level.

As I found out, you can also compost leaves in a bag. I happened to use paper, which allowed air and water in as the paper decomposed. However you could even use plastic garbage bags, as long as you cut or tear openings in the bag for venting. You’ll also need to check the contents periodically to make sure they are not drying out.

How Long Does It Take?

Since leaves are considered a “brown” composting material and are predominantly carbon, they can take longer to decompose than an active compost pile. An unstructured pile can take up to two years, but in a bag or a 3 ft. x 3 ft. bin, you should see results within 6 - 10 months, depending on the weather and the types of leaves.

If you’re impatient, you can shred the leaves before composting them. This will greatly speed the process. If you don’t have a shredder, just run the mower over them. You should ideally turn or toss the pile every month, to ensure the leaves are decomposing evenly throughout. I don’t usually bother and it hasn’t slowed things down too much.

Using Leaf Mold in the Garden

Leaf mold is considered a soil conditioner. Although it doesn’t add much in the way of nutrients, leaf mold improves soil’s structure, texture and water-holding ability. It also creates ideal conditions for establishing a soil ecosystem of beneficial organisms.

Consider leaf mold a free and renewable alternative to peat, with even better water retention. Leaf mold can hold several hundred times its own weight in water and soils amended with leaf mold improved their water holding ability by almost 50 %.  Working 3 in. of leaf mold into the top 6 in. of soil can improve the water holding capacity of sandy soil 2 ½ times.1

In addition to improved water retention, it also helps to loosen heavy soils.

Garden soils amended with leaf mold actually approach that elusive “well-drained, moist soil” that is so often recommended.

You can work leaf mold into your soil, the same way you would compost. Just add a layer of 2 - 4 in. of leaf mold and either turn it into the top 6 in. of soil or simply let it set and wait for the earthworms to do the work for you. You can also side dress with leaf mold, ringing the periphery of plants with a couple of inches the stuff. Just be careful not to pile it up against the plant stems.

All of these findings are from a study done at the Connecticut Agriculture Experiment Station.  They go on to say that adding a 1 in. layer of leaf mulch on top of your garden bed each year could eliminate the need for fertilizer, although their ideal recommendation it leaf mold plus inorganic fertilizer at half rate.

One last tip, don’t be shy about asking your neighbors for their unwanted leaves. If they’re going to rake them to the curb for pick-up, chances are good they’ll be happy to have you come by and rake them up first.        

More on Improving your garden soil:

Soil pH | Soil Amendments | What is Organic Matter? | What is Green Manure? | Is Your Soil Ready to be Worked?

1Research Resources: