Q: I have several large oak trees that cover my garden with leaves every fall. I’m trying to reduce disposal costs by reusing them as mulch in our landscape, but they fly around and make a mess. Someone told me I could turn them into leaf mold but I’m not sure what that means. What is leaf mold and how can I use it in my garden?
ONE: A strong Leave the Leaves movement has emerged over the past decade. People are getting the message that fallen leaves provide a variety of benefits for landscape plants and wildlife. Plus, skipping the tasks of raking, bagging, and hauling leaves can save time and money. But as you’ve noticed, leaving foliage behind in the garden comes with other challenges.
Composting oak leaves into leaf soil is a great way to avoid the expense and hassle of leaf disposal and give your lawn the benefits of recycled leaves while keeping it clean and tidy.
What is leaf mold?
Leaf mold is the dark, crumbly, sweet earthy-smelling compost that comes from decomposing deciduous tree leaves. It is naturally deposited in thin layers on forest floors each year, where it supports a diverse community of soil-dwelling microbes, insects, worms and plants. Leaf mold significantly improves the structure of sandy or clay soils. This bulky organic matter increases the soil’s water holding capacity, aeration, drainage and nutrient buffering capacity, among many other minor benefits.
Unlike traditional compost, which breaks down quickly in a heat-generating bacterial process, the leaves decompose slowly in cool, damp conditions and are fueled almost entirely by fungi. Making leaf soil is far less labor intensive than traditional composting, but requires a little more space and can take up to a year or more. Leaf mold works well when applied to the soil surface or plowed into the top 2 inches of soil.
Related: 9 Types of Mulch to Keep Your Landscape Lush
Leaf mold is a superior soil amendment when it comes to moisture retention.
Leaf mold acts as a water reservoir in the soil. The porous organic material absorbs water and creates narrow capillary spaces in the soil, enhancing water movement. The spongy texture efficiently traps excess moisture when it’s available, then slowly releases it when conditions are dry.
Leaf mold has been shown to increase the soil’s water-holding capacity by up to 50 percent. Applying a 1- to 2-inch coat of leaf mold annually is like buying drought insurance. You can water less frequently and even the driest weather will affect your plants less.
Unlike regular compost, leaf mold does not contain many beneficial nutrients for plants.
Despite all the structural benefits that leaf mold offers, it does not add any significant nutritional value to the soil. Although fallen leaves initially contain significant traces of nitrogen, calcium and numerous other nutrients, these valuable resources are not carried over into the final product. The organisms that break down leaf cellulose consume much of the nutrient content, leaving behind stable, bulky organic matter.
Leaf mold does not replace fertilizer, but it creates an environment where plants can use both conventional and organic fertilizers more efficiently, with less potential for runoff pollution. The improved soil structure and added organic matter provide better habitat for microbes that consume, store and transfer nutrients to plants.
Related: This lawn fungus might be lurking under the snow in your yard
The type, size and condition of the leaves affect the decomposition rate.
The time it takes to make a batch of leaf mold can vary from 6 months to 2 years. Several factors play into the time required, including the type, size and condition of the leaves. Type and size are related, as broadleaf evergreen leaves, like southern magnolia and holly, are thick and resistant to rot.
Decomposition is enhanced by an increased surface area. Smaller, thinner leaves offer more surface area per volume compared to larger, thicker leaves, so they break down faster. For faster results, shred the leaves before processing.
The condition of the leaves also plays a role. If they fell in October and were collected in January, they have already started the process of decomposition, reducing the time to a full batch. Moisture is extremely important to the process, so it’s best to start with wet leaves.
How to make leaf shape
Crafting Leaf Form is easy and mostly passive – plus it’s fast. Some gardeners simply apply 12- to 24-inch layers of leaves as a mulch to landscape and garden beds and allow them to decompose. But as mentioned above leaves are blown around. For better control with a little more work, leaves can be gathered to form a leaf shape pile. How to make leaf mold in just a few easy steps:
- Create an enclosure. It’s possible to just pile up the leaves, but a leaf compost bin will help keep the leaves from blowing around. Cut a 4 foot length of wire or nylon fencing (about 19 feet for a 6 foot circle or 13 feet for a 4 foot circle). Fix it in a circle and put it in a shady place.
- collect the leaves. Whole leaves will decay over time, but crushed leaves decompose more quickly. Use a lawnmower with a digger attachment to shred and collect the leaves all at once, or stack them and use a leaf shredder to shred them into an even finer texture.
- Fill the enclosure. Pack the leaves into the enclosure. For the fastest decomposition, moisten the sheets as they are stacked. If leaves are falling in your area for a long period of time, it’s okay to add more leaves in batches; The heap will shrink as it decomposes.
- Moisten and cover the pile. When the container is full or when all of the seasonal leaves have been collected, wet the outer surface again. Then cover the pile with a tarp to retain moisture and block sunlight.
- Harvest leaf mold. After a year, check the stack. Leaf mold is ready to use when it is dark brown, soft and crumbly. The pile often has an outer layer of dried leaves surrounding the inner pile of the finished leaf form. If this is the case, peel off the outer layer for further processing and harvest the finished product.
See also: Composting 101 – How to use kitchen and garden waste in your garden
The best ways to use leaf mold in your home interior
Leaf mold is an ideal mulch and soil amendment for many of the most common gardening applications. Whether you grow plants in containers or in the ground, it serves as a superior alternative to store-bought products like peat moss and coco. (And it’s free.)
Because leaf mold has not been processed and sterilized, it adds a dimension of biological activity to the plant root zone. It contains soil-forming fungi that further process the coarse organic matter in the soil, and it attracts beneficial insects and earthworms that help with soil formation and aeration. Below are some popular uses for homemade leaf mold compost.
- Incorporate a 2-inch layer of leaf mold into the top 2 or 3 inches of garden beds for an instant boost. It works equally well for improving the texture of sandy or loamy soils.
- Apply a 2- to 4-inch layer of black leaf mulch to perennial and vegetable beds. Earthworms and other soil dwellers carry it deep into the soil to produce noticeable improvements over time.
- Use leaf compost as the base material instead of peat or coco in homemade potting soil. Add equal parts leaf mold and perlite for a fluffy, earthless mix.
- When weeds have overgrown a garden bed, use leaf mold to reclaim the space. Cut the weeds at ground level and let them cook in the hot sun for a day. Cover the stressed weed bed with cardboard or thick paper. Apply a 4 inch coat of leaf mold on top and wait 4 weeks before planting new plants or sowing garden seeds.