Nature’s Gold: Don’t Throw Those Leaves Away
By Gail Goldberger
The Morton Arboretum
The next time you find yourself up to your ankles in leaves, wondering whether to blow or bag them, stop. Use them instead.
Left to their own devices, deciduous trees lose leaves to the ground, returning their own nutrients to the soil for enrichment. Consider our natural woodlands or national forests. No one rakes, blows or collects leaves in these places. Rather, they are left to lie, decomposing where they fall, melding their remains back into the earth.
We should take our cues from nature. The best mulches and fertilizers for plants, flowers, and trees are right under our noses, at our feet to be exact. They don’t cost anything either.
Leaves are highly beneficial to soil, for their nutrient and moisture content, and because they insulate soil from temperature fluctuations. If leaves happen to blow over ground covers and perennials, leave them there, for these plants will also benefit from decomposition. Just be sure the leaf layer is not too thick or it could suffocate plants.
Leaves aren’t usually a problem for shrubs either, as they’ll tend to be held in place on the ground. But under trees, whole leaves can blow away. For this reason, it’s best to prepare leaves for use.
Try mowing them. This pulverizes the leaves - grinding them into finer particles that will decompose more quickly than when the leaves are left whole. The particles will drop between the blades of grass and provide nutrients for your lawn. Or collect the shredded leaves, and scatter them wherever you want mulch: under your tree, or over your flower beds, vegetable gardens or around perennials. Mix the particles with other organic materials if you need to give them weight.
You can also collect leaves or leaf particles in a porous container that allows air to get through, where they can sit until spring or summer. They can sit alone, or be combined with composting materials such as grass clippings, weeds, conifer needles, straw, flowers, or brush and shrub trimmings. By the time winter passes, the leaves will be on their way to becoming nutrient-rich compost.
Some people go even further and combine food waste (except dairy, meat or fish) with leaves, weeds and clippings. This forms the basis for compost, which can be plowed back into soil for a good growing medium for flowers, plants, or fruit and vegetable gardens. Composted soil is more fertile and its looser texture allows more oxygen to reach tree and plant roots.
Bear in mind that mowing, mulching and composting leaves are particularly good practices for urban areas, where soil is often compacted in restricted growing areas, and compromised by construction materials. The Morton Arboretum also recommends leaf reuse for new subdivisions, where soils may not have had the opportunity to be enriched by the leaves of older, established tree communities.
Glad You Asked
Q. Are some leaves better for the soil than others?
A. All leaves are good, but oak leaves may be more acidic when reasonably fresh, lowering the pH of the soil, but as they decompose they become more alkaline (typical of our Midwest soils). Continuous use of oak leaves will, however, keep soil more acidic which is good for rhododendrons and other acid-loving plants.
Q. Why do I always have more leaf litter than my neighbors?
A. You must have trees with a higher leaf area index, or a higher density of leaves in the crowns, such as maple or oak. This is a good thing. More leaves mean that your trees provide more environmental benefits. Trees with high leaf area indices intercept more storm water, provide more shade, absorb more carbon dioxide and other air pollutants, and provide other benefits as well.
Gail Goldberger writes for The Morton Arboretum.