Foliage season is a mixed blessing. I have one eye on the gorgeous spectacle of changing colors and the other eye on the value of these leaves—and how I can put them to work.
As the autumnal equinox approaches, trees that were just beginning to show some color yesterday will soon be brown and on the ground, their brief moment of glory gone.
Free Soil Amendment
Look at all those leaves as brown gold. The leaves of one large tree can be worth as much as $50 worth of plant food and humus. They are a rich source of calcium, magnesium, phosphorus, potassium, and trace minerals the tree roots have mined from deep in the subsoil. Pound for pound, leaves contain twice the mineral content of manure. The huge amount of organic matter they offer can be used to improve soil structure. Leaf humus can lighten heavy clay soils and increase the moisture retention of dry sandy soils. No organic gardener should pass up this opportunity for a free soil amendment.
If you are not already composting, now is a good time to start. Rake or blow your leaves into loose piles or enclose them in bins, if you wish.
If you want to speed up decomposition, mow over the leaves a few times with your lawn mower or shred them into smaller pieces with a leaf shredder or chipper. Many leaf vacs have a shredder in them to reduce the volume of the leaves being inhaled. Mix a shovelful of soil in each layer of leaves to introduce helpful microorganisms to the pile. Leaves are high in carbon but low in nitrogen so it helps to add a source of nitrogen like manure or grass clippings to help feed the bacteria that will be doing all the work of breaking down the leaves. Spent plants from the garden that were not diseased or infested with insects can be added to the pile along with kitchen scraps.
Shredded leaves also make a good mulch. Just blow them into your flower beds and under trees and shrubs while mowing. I use a lightweight no-noise leaf blower for my chores now; it’s just so much quicker.
We cover the beds in our vegetable garden with a layer of chopped leaves to keep the soil from washing away over the winter. The best time to mulch perennials is after the ground has frozen, so put aside another pile of shredded leaves to use later in the fall.
Improve the Soil
Don’t want to rake or blow your leaves at all? Researchers at Michigan State University have proven that mowing leaves and leaving them on your lawn improves the soil, lessening the need for fertilizer in the spring. They recommend setting your mower blade 3 inches high and mowing once a week while the leaves are falling.
Need another excuse not to pick up those leaves? Fallen leaves help create mini-ecosystems for worms, fungi, and soil bacteria. They may take a few years to rot away but they will be feeding countless microorganisms, and sheltering insects, reptiles, and amphibians. Leaf litter provides a welcome source of insects and seeds for birds and other wildlife too so don’t fret if you don’t get around to leave clean-up.