Hello Mid-Ohio Valley farmers and gardeners! I see many homeowners clearing leaves this fall around the valley. Why not collect these leaves to make leaf mold, a valuable compost?

This week I want to discuss composting leaves to make leaf mold, otherwise known as black gold. Leaves are a natural soil builder, can reduce the need for fertilizer in lawns and gardens, and provide excellent winter insulation for plants. Leaf mold is a nutrient-rich soil amendment produced by the fungal decay of tree leaves.

However, unlike traditional compost, which undergoes a heat-generating process driven by bacteria, leaf mold is produced through a cooler and much slower process driven by fungi. The resulting decomposed material is an excellent soil additive. It can be mixed in during tillage or used as a surface mulch for no-till gardening.

Leaf mold is different from other compost. Tree leaves are high in carbon and low in nitrogen compared to other compostable materials. For this reason, tree leaves cannot be conventionally composted without the addition of nitrogen-rich material to increase the carbon/nitrogen ratio.

The high ratio of carbon to nitrogen is also the reason why growing the leaves directly in the soil is not recommended. Microorganisms in the soil will use the nitrogen in the soil in an effort to break down the leaves, leading to nitrogen deficiency in the plants. However, given adequate time and moisture, the separate fungal decomposition of the leaves results in excellent material that can be added to the soil.

The easiest way to take advantage of all the nutrients the leaves have to offer is to gather them and let them sit. If you already have a compost bin, but have more leaves in the fall than your bin can handle, store the remaining leaves in bags or bins.

Shredding first can save a lot of space. Depending on how finely the leaves are shredded, they can take up to one-sixteenth the space of whole leaves.

A simple pile is effective, or a wire compost bin can be used to better contain the leaves. The leaves should be moist, but not wet, to provide adequate humidity for the fungus. Let the pile compost or “mold” for two years before use. Usually, a healthy dose of the fungus to create leaf mold is already present in the autumn leaves. This is what triggers the decomposition process.

You can speed up the process by cutting the leaves with a lawnmower before you pile and/or turn the pile occasionally. This will increase the speed and uniformity of the leaf casting process, and the leaf mold will be ready in about a year. Properly maintained, a compost pile does not smell.

Leaf mold adds valuable organic matter to the soil. This natural soil conditioner improves water holding capacity and improves soil structure. Research has shown that leaf mold and other composts can increase crop yields, improve plant health, and even increase a plant’s resistance to disease.

As a mulch, leaf mold moderates soil temperature and reduces evaporation. Use the compost when setting up new plants or spread it over your flower gardens in the spring.

There are a few types of leaves that homeowners don’t want to compost into leaf mold. Because of allergic reactions, throw away poison ivy, poison oak, and poison sumac leaves rather than risk the adverse effects of handling them. Do not use black walnut leaves which contain juglone and can inhibit plant growth.

It is also good to know that beech, birch, hornbeam, sweet chestnut, magnolia and holly leaves all contain large amounts of lignin and should be shredded before composting to speed up their decomposition into leaf mold.

When finished, the leaf mold should be dark and have an earthy smell and be ready to enrich the soil.

Contact me at the Wood County WVU Extension Office 304-424-1960 or email me at [email protected] with questions. Until next time, good luck and happy gardening!