Don't Throw Away Autumn: What Fallen Leaves Can Do for Your Garden

  

Every autumn, nature delivers one of the finest soil amendments available—and then we spend a surprising amount of time raking it up, stuffing it into bags, and hauling it away.

Fallen leaves are not garden waste. They are part of the garden.

Walk through an old hardwood forest and consider what happens there. No one bags the oak leaves. No one carts away the hickory and maple leaves. Year after year, they fall, accumulate, decay, and return their nutrients to the earth. Beneath them lies that dark, crumbly woodland soil gardeners are forever trying to imitate.

Your garden can benefit from the same ancient process.

Leaves Are Nature's Mulch

A layer of fallen leaves protects the soil much as mulch does. It moderates temperature, reduces evaporation, cushions the earth against pounding rain, and helps suppress weeds.

This is particularly useful going into winter. A covering of leaves can help protect the crowns and shallow roots of perennial plants from sudden swings in temperature. In the South, where winter weather can seesaw from shirtsleeves to hard frost in a matter of days, that insulation can be especially valuable.

Whole leaves can sometimes mat together, particularly large leaves such as sycamore or magnolia. Running them over with a lawn mower or shredding them before use produces a looser mulch that admits air and water more readily.

Spread shredded leaves a few inches deep around shrubs, trees, and established perennials, keeping them slightly away from trunks and crowns.

And there you have it: mulch that costs nothing but a little autumn labor.

Feed the Soil, Not the Landfill

Leaves contain nutrients that trees have drawn from the soil during the growing season. As those leaves decompose, some of those nutrients become available again.

Just as important is their organic matter.

Organic matter helps improve soil structure. In sandy soil, it increases the soil's ability to retain moisture and nutrients. In heavy clay, it helps create a more open, workable structure. Over time, decomposing leaves contribute humus—the dark organic material associated with fertile, living soil.

Throwing leaves away interrupts that cycle.

Keeping them on your property allows some of what the trees borrowed from the earth to return home.

Make Leaf Mold

One of the simplest uses for autumn leaves is also one of the best: make leaf mold.

Despite the rather unappetizing name, leaf mold is wonderful stuff. It is simply leaves allowed to decompose, primarily through fungal activity, until they become a dark, soft, earthy material resembling woodland humus.

Making it can be remarkably uncomplicated.

Pile leaves in an out-of-the-way corner, place them in a simple wire enclosure, or collect them in a ventilated container. Shredding the leaves first will speed decomposition, and keeping them somewhat moist will help.

Then wait.

Nature is not in a hurry.

Depending upon the leaves, moisture, climate, and degree of shredding, the process may take a year or more. The finished leaf mold can be worked into garden soil, spread around plants, or used as a soil-conditioning mulch.

It is especially useful for improving the soil's ability to hold moisture.

Add Leaves to the Compost Pile

Autumn leaves are also excellent "brown" material for compost.

Kitchen scraps, fresh grass clippings, and other green materials tend to be relatively rich in nitrogen. Dry fallen leaves provide carbon. A mixture of the two creates better conditions for decomposition than either material alone.

This presents an opportunity worth planning for.

Instead of putting every autumn leaf into the compost pile at once, save some dry leaves in bags, bins, or a covered enclosure. During the following months, add handfuls or layers whenever you add kitchen scraps or other nitrogen-rich material.

In effect, autumn can provide part of your composting supplies for the entire year.

Shredded leaves decompose more quickly, but whole leaves will eventually break down too. The microbes are patient even when gardeners aren't.

Leave Some Leaves for Wildlife

There is another reason not to make the autumn garden too tidy.

A layer of fallen leaves provides habitat for an astonishing assortment of small creatures. Beneficial insects, spiders, beetles, caterpillars, and other organisms may overwinter among fallen leaves or beneath them. Some moths and butterflies spend part of their life cycles in leaf litter.

Birds know this very well.

Watch a brown thrasher, towhee, or other ground-feeding bird scratching through leaves. It isn't admiring your landscaping. It is looking for supper.

Removing every leaf from every corner of the property can remove some of the shelter and food sources upon which these creatures depend.

That doesn't mean your front walk needs to disappear beneath six inches of oak leaves. There is room for order and stewardship together. Clear the lawn, paths, gutters, and places where heavy accumulations might cause problems, but consider leaving leaves beneath trees, around woodland borders, and in less formal portions of the garden.

A garden need not look abandoned to remain alive.

What About Leaves on the Lawn?

A light scattering of leaves can often simply be mowed into the lawn. A mulching mower chops them into small pieces that settle between the grass blades and gradually decompose.

A thick blanket is another matter.

Heavy layers of whole leaves can block sunlight and air, hold excessive moisture, and smother turf. If you cannot see much grass beneath the leaves, it is probably time to rake, mulch, or collect some of them.

But "collect" needn't mean "discard."

Move them to flower beds. Put them beneath shrubs. Compost them. Make leaf mold. Store them for later.

There is almost always somewhere better for a leaf than a garbage bag.

A Word of Caution

Not every fallen leaf should necessarily be returned directly to the garden.

If plants have suffered badly from certain diseases, infected foliage may harbor organisms capable of causing trouble again. Good sanitation can be an important part of disease management. When dealing with seriously diseased material, determine whether composting, disposal, or another treatment is appropriate for the particular disease.

Also avoid piling leaves thickly against tree trunks, shrub stems, or the crowns of perennials. Mulch should protect plants, not bury them.

As with most things in gardening, moderation and observation are better guides than rigid rules.

The Old Way Wasn't So Foolish

Before plastic bags, municipal leaf collection, and truckloads of commercially packaged soil amendments, gardeners had little reason to regard leaves as rubbish.

They composted them. They piled them. They dug them into gardens. They allowed them to rot beneath shrubs and trees. They understood something that modern convenience can make easy to forget:

A garden produces many of the materials needed to sustain itself.

The leaves falling across your yard this autumn are part of next year's garden.

They can become mulch around your perennials, carbon for your compost pile, shelter for overwintering creatures, organic matter for tired soil, and eventually the dark humus from which new roots will grow.

So rake where you must. Shred where you can. Compost some. Pile some. Leave some beneath the trees.

But don't throw away autumn.

The garden has spent an entire season making it for you.

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