Autumn always seems to sneak up on us. Finally, drier days and cooler nights replace the heat and humidity of summer. Here and there is a glimpse autumn colors peeking out of the green landscape. Then, just as we're beginning to enjoy them, those warm hues are replaced by dismal browns as leaves carpet our lawns and gardens.
This leaf-shedding process, known as abscission, has actually been occurring for several weeks. Cells, located at the spot where the leaf stem is attached to the tree, toughen and begin to form a protective waterproof scar. The cells in the leaf stem itself swell, weaken and degenerate. This interferes with the flow of moisture and nutrients into the leaf, reducing the production of a pigment, known as chlorophyll, which gives leaves their green color.
As the days shorten, there is less sunlight energy to manufacture food. Nutrients and minerals are withdrawn from leaves and transported to the permanent parts of trees such as the trunk, stems and roots. Chlorophyll breaks down. But leaves also contain other pigments that give them their fiery fall colors. These other colors are hidden most of the year by the abundance of chlorophyll, making leaves appear green. As chlorophyll breaks down and other pigments are unmasked, leaves reveal their autumn colors.
The final step in the abscission process occurs when a tree sheds its leaves. Gradually, the bond between leaves and a tree weakens. The tiny veins that carried sap to the leaves all summer long are sealed off. Leaves then fall to the ground, encouraged by wind or by the sheer weight of gravity. Now, what to do with all those leaves?
Many communities recycle yard wastes, creating mulch from branches and compost from leaves and grass. This is great and saves landfill space. But those who detest the laborious work of raking and bagging leaves (like me!) might consider a few alternatives.
One of the most ecological and economical way to manage fallen leaves is to compost them. As the leaves decompose, they release nutrients back into the soil. If you have a mulching mower, leaves can be cut into smaller, faster-decomposing pieces. Mulched leaves can be left on lawns and will actually enhance the soil, reducing the need to fertilize the yard next spring.
Leaves can also be composted. Composting is the decomposition of organic materials by microorganisms. The result is a recycled, earthy- smelling, soil-like material that can be added to a yard to provide nutrients. Carbon and nitrogen in composted plant cells provide fuel for microorganisms. Nitrogen provides the raw material of protein to build their bodies. The ideal mix for a compost pile is two parts of "greens" for nitrogen (grass and food scraps) to one part of "browns" for carbon (leaves, straw and woody materials).
Those who have a lot of trees and more leaves than can be mulched can spread them around vegetable gardens, flower beds, bushes and trees. Not only does this contribute nutrients to these areas, but the leaves also form an insulating barrier around plants, reducing moisture loss and damage from severe winter weather.
Composting leaves saves time and money. Soil covered by composted mulch is less likely to erode. Composting leaves or applying them to gardens reduces the need to fertilize. This cuts down on the amount of nutrients that run off the land into streams and rivers and, ultimately, the Chesapeake Bay. Of course, leaves are good for other things too. Nothing beats jumping into a big pile of leaves on a crisp autumn day!
For information about leaf management and backyard composting contact:
DE Cooperative Extension
New Castle County 302-831-2667
Kent County 302-730-4000
Sussex County 302-856-7303
MD Cooperative Extension
PA Cooperative Extension
VA Cooperative Extension
www.ext.vt.edu or 540-231-4310