Leaves Are Treasure, Not Trash

Keep the Leaves

If you have mature trees in your landscape, every autumn those trees present you with a gift of great value. For some, those leaves may seem like an unwanted nuisance, piling up in your beds or on your lawn, a battle to be fought and won when your local municipality or trash hauler takes them away. We, even scientists and researchers, use unflattering terms, leaf "litter" or "duff", to describe them.

It seems strange that in the fall, we rake leaves to put into plastic bags or to the curbside to be hauled away for disposal somewhere else, at a cost to us, and then in the spring, we spend more money on plastic bags of mulch or compost to add to our garden. Or, we go to a local facility to haul home compost sourced from many different places. The problem with that? You do not know the quality of that compost or what may be in it – contaminants, trash, or pests, such as invasive earthworms, that you will regret introducing into your landscape.

It is time to rethink our attitude towards leaves, for the benefit of our own gardens as well as that of the surrounding environment and its inhabitants. If you have the leaves available, why not use what nature provides to restore the natural process of plant nutrient recycling in your yard? If the wind blows leaves from your neighbor's yard into yours, why not thank your neighbors for the free garden gold? Leaves, with some patience but very little effort on your part, can be turned into an excellent soil amendment or mulch that costs nothing but is worth everything to your plants.

There are two basic approaches to recycling leaves. One is shredding the leaves to make mulch or to let them break down into the lawn, and the other is piling whole leaves to transform into leaf mold. From the standpoint of effort and the environment, the latter approach is preferable, but either method is better than removing the leaves from your property.

Shred the Leaves

For shredding leaves, a lawn mower is the only tool needed. A mulching mower works best, but a regular mower will do the job, although not quite as effectively. Simply mow over the leaves on the lawn to shred them, walking or riding slowly to give the mower blades time to chop the leaves. This is easier to do if the leaves are relatively dry and not piled too thickly, so do not wait until all the leaves have fallen to start mulch-mowing them. You may need to go back over the leaves in a cross direction from the first cut to shred the leaves more finely. A layer up to about one-half inch in depth is beneficial to the lawn.

Shredded leaves decay much more quickly than whole leaves. The small leaf pieces on the lawn break down, adding organic matter and returning essential plant nutrients to the soil to be taken up by the grass. Research conducted at Michigan State University found no negative effects of mulching leaf litter into the turf. The quality of the grass improved, with fewer broadleaf weeds; the quality of the soil improved, even to the extent of providing a softer surface for sports; and it had no effect on the soil pH, whether oak or maple leaves were used.

Shredded leaves can also be applied as a 2 to 4-inch-thick layer of mulch around trees and shrubs or on perennial beds. Because they are shredded, they tend to mat down less than whole leaves; and watering the leaf mulch after application will also help it to stay in place. The leaf mulch will help to moderate soil temperatures, retain soil moisture, and keep down weeds. Weeds that do appear are easier to pull because the soil surface remains friable and soft. As the leaves break down, essential nutrients are recycled in the soil to become available again to the plants from whence they came.

Pile the Leaves

The second method of recycling leaves is turning them into leaf mold. Essentially decayed leaves, leaf mold is similar to compost; it is dark brown in color, with a pleasant earthy smell and a crumbly texture. Although it is not high in nutrients, it is an excellent soil amendment that improves the structure of the soil, increases soil water retention, returns essential elements to the soil, and benefits the myriad organisms in the soil – fungi, bacteria, and other microbes, as well as tiny mites and insects – that decompose organic matter. It can also be used as mulch or added to potting soil. And unlike compost or manure, leaf mold is mostly weed-free.

To make leaf mold, form a pile of leaves, pack them down, water them, and wait a couple of years. Although not essential, a wood or wire bin, 3 to 6 feet in diameter and at least 3 feet in height, helps keep the leaves contained. Another possibility is to use a large plastic bag; I use old trash cans. Fill the bag or can with leaves, moisten the leaves, close it up loosely (allow some airflow), and let it sit.

You can also just pile excess leaves in an out-of-the-way corner of the yard. However, if you have a wooded area that already has a layer of fallen leaves, do not pile more leaves on top of that. There are many small insects and animals, including firefly larvae, overwintering insects, reptiles, amphibians, birds, and small mammals, that make use of that leaf layer for shelter, habitat, food, and protection. Dumping more leaves can disturb or disrupt the natural depth (6 to 12 inches) at which they survive.

If you have a compost bin, you may have too many leaves in the fall to fit in the bin, so stockpiling those leaves in a separate pile is a good way to save this valuable resource. In the spring and summer, you can transfer some of your leaf stockpile into your compost bin as you need "brown" materials to layer with fresh "green" materials; the remainder of the leaf stockpile will gradually shrink in size as the leaves slowly decay to form leaf mold.

You can speed up the decay process from years to 6 to 12 months by shredding the leaves, turning the pile occasionally, adding water occasionally, or covering the pile with a tarp, but it will happen eventually, even if you do nothing.

Making leaf mold is outrageously easy. It is a task that rewards the lazy gardener (like me) and teaches the patience of nature (or the nature of patience) to the impatient gardener. For every gardener, autumn leaves on and off the tree are not just pretty, they are a gift of nature waiting to happen.