(Released 20 November 1997)
B. Rosie Lerner
Purdue Extension Consumer Horticulture Specialist
The recent Arctic blast that visited our area made for a rather dramatic leaf fall in many neighborhoods. With large quantities of leaves blowing around their yards, some people may be tempted to resort to the old-fashioned and effective method of burning.
However, in addition to being illegal in many areas, leaf burning leads to air pollution and is a health and fire hazard. The smoke from burning leaves contains a number of toxic and/or irritating particles and gases. The tiny particles contained in smoke from burning leaves can accumulate in the lungs and stay there for years. These particles can increase the risk of respiratory infection, as well as reduce the amount of air reaching the lungs. For those who already suffer from asthma and other breathing disorders, leaf burning can be extremely hazardous.
Moist leaves, which tend to burn slowly, give off more smoke than do dry leaves. These moist leaves are more likely to also give off chemicals called hydrocarbons, which irritate the eyes, nose, throat and lungs. Some of these hydrocarbons are known to be carcinogenic.
Carbon monoxide is an invisible gas that results from incomplete burning, such as with smoldering leaf piles. After inhaling carbon monoxide gas, it is absorbed into the blood, where it reduces the amount of oxygen that the red blood cells can carry. Children, seniors, smokers and people suffering from chronic lung and heart disease are more susceptible than healthy adults to carbon monoxide effects.
I hope these facts have convinced you to not burn your leaves, but what are the alternatives? Those of us lucky enough to have municipal pickup of leaves for composting can simply rake the leaves to the curb, or bag them if appropriate. But what are the rest of us supposed to do with all these leaves?
You could compost those leaves yourself. Dry leaves alone will break down slowly over time, but you can speed that process by mixing the leaves with green plant materials, such as grass clippings, garden discards and produce scraps. Or you could add a source of nitrogen, such as livestock manure or commercial fertilizer. Mix (turn) the pile occasionally to keep a good supply of air in the compost. A good-sized compost pile should be a minimum of 3 cubic feet. The compost will be ready to use as a soil conditioner in several weeks to several months, depending on size and management techniques.
Shredded leaves also can be used as a mulch around garden and landscape plants. Mulches provide many benefits, including weed suppression, moisture conservation and moderation of soil temperature. Leaves can be applied to dormant plants in winter to prevent young plants from heaving out of the ground. Leaf mulch can help keep soil cooler in summer. No more than a 2- to 3-inch layer of leaves should be used around actively growing plants. Chopping or shredding the leaves first will help prevent them from matting down and preventing air from reaching roots.
Directly applying the leaves to a garden or unused area of soil is another option. Try to spread the leaves over as large an area as possible, then till or plow them under. Chopping or shredding the leaves first will help them to break down faster.
My personal favorite option is to simply shred the leaves through my lawn mower until the pieces are small enough to just leave them right there on the lawn! Dry leaves are much easier to handle through the mower than moist ones. If possible, remove the bagger so all of the leaves are deposited right back onto the lawn as they shred.
The URL for this page is http://www.hort.purdue.edu/ext/burnleaves.html