Mike Travis, UW-Extension Pepin County Agriculture Agent

WHAT IS LEAF MOLD? Leaf mold is essentially “composted” shade tree leaves. However, unlike

traditional compost that undergoes a heat-generating, bacterially-driven process,

leaf mold is produced through a cooler and much slower fungal-driven process. The

resulting decomposed material is an excellent additive to soil. It can be mixed in during tillage, or used as a surface mulch for no-till gardening.

HOW IS LEAF MOLD DIFFERENT THAN OTHER COMPOST? Tree leaves are high in carbon and low in nitrogen compared to other compostable

materials. The carbon to nitrogen ratio (C:N) is typically 60:1. The C:N ratio to

support ideal bacterial decomposition is 24:1. Because of this, tree leaves cannot

be conventionally composted without adding a nitrogen-rich material to increase the C:N ratio. The high C:N ratio is also the reason that tilling leaves directly into

soil is not recommended. The soil microorganisms will use up the soil nitrogen in

an effort to break down the leaves, which leads to nitrogen deficiency in plants.

However, given adequate time and moisture, separate fungal decomposition of

leaves results in an excellent material that can be added to the soil.

WHAT ARE THE BENEFITS OF LEAF MOLD FOR MY GARDEN? Leaf mold adds valuable organic matter to the soil. This natural soil conditioner improves water-holding capacity, enhances soil structure (and therefore water and

air movement within the soil), and provide habitat for the soil’s micro– and macro–

organisms. Research has shown that leaf mold and other composts can increase

crop yield, improve plant health, and even enhance a plant’s resistance to disease.

As a mulch, leaf mold moderates soil temperature and reduced evaporation. Our

growing understanding of soil health principles underscores the value of natural organic materials such as leaf mold in plant health and productivity.

Heckman, J. R., & Kluchinski, D. (1996). Chemical composition of municipal leaf waste and hand-collected urban leaf litter. Journal of environmental quality, 25(2), 355-362.

Maynard, A. A., & Hill, D. E. (2000). Cumulative effect of leaf compost on yield and size distribution in onions. Compost Science & Utilization, 8(1), 12-18.

Zhang, W., Dick, W. A., & Hoitink, H. A. J. (1996). Compost-induced systemic acquired resistance in cucumber

to Pythium root rot and anthracnose. Phytopathology, 86(10), 1066-1070.

Heckman, J. R., & Kluchinski, D. (2001). Agronomics of land application of municipal collected shade tree

leaves: I. Soil properties. Journal of Sustainable Agriculture, 17(2-3), 33-40.

is a nutrient-rich, valuable soil amendment produced through fungal decomposition of tree leaves.

MAKING & USING LEAF MOLD Collect, pile, moisten. A simple pile is effective; a wire compost bin can be used to better contain the leaves. The leaves should be moist, but not wet, to provide adequate moisture for the fungi. Let the pile “mold” for two years before using. You can speed the process. Chop the leaves with a lawnmower before piling, and/or occasionally turn the pile. This will increase the speed and uniformity of the leaf molding process. The leaf mold will be ready in about a year. Add to soil. Leaf mold can be tilled into soil, however, a 2-inch layer is an effective mulch for a no-till garden. Add leaf mold to the soil surface; worms and micro-organisms will incorporate the humus and nutrients into the soil. Or, skip the leaf mold process and sheet mulch with “raw” leaves. They will naturally cure in-place.

is a valuable resource for building soil health through organic matter,

biological activity, and mineral

nutrients.

July 2017