Mulch Them in Place/Mow Them

Leaves are rich in carbon, phosphorus, and potassium - all essential nutrients needed by plants including turf grasses (Wisconsin Department of Natural Resources).  Simply mow your leaves along with the grass during fall, and let the small leaf pieces filter down among the grass blades.  Make sure grass is exposed to the sun after the tree leaves have been mulched.

Why Mulch in Place?

• It reuses essential plant nutrients contained in tree leaves.

• It saves the time, trouble, and expense of raking or bagging leaves.

• It does not adversely affect turf quality.  According to studies performed at Michigan State University, "... there have been no meaningful differences observed in turf quality ratings, turf density, thickness of the "thatch" layer, amount of organic matter in the "thatch" layer, or the number of dandelions in the plots."  In fact, in recent studies, turf receiving mulched tree leaves greened up faster in the spring and required less fertilization the next season.

• It reduces smoke caused from burning leaves. 
  
  The following information on the health hazards of burning leaves is from the Wisconsin Department of Natural Resources. 
  
  The smoke generated by a large number of simultaneous leaf fires can cause significant health problems. Leaf smoke can irritate the eyes, nose and throat of healthy adults. But it can be much more harmful to small children, the elderly, and people with asthma or other lung or heart diseases. This is because the visible smoke from leaf fires is made up almost entirely of tiny particles that can reach deep into lung tissue and cause symptoms such as coughing, wheezing, chest pain and shortness of breath--symptoms that might not occur until several days after exposure to large amounts of leaf smoke.
  
  Besides being an irritant, leaf smoke contains many hazardous chemicals, including carbon monoxide and benzo(a)pyrene. Carbon monoxide binds with hemoglobin in the bloodstream and thus reduces the amount of oxygen in the blood and lungs. So carbon monoxide can be very dangerous for young children with immature lungs, smokers, the elderly, and people with chronic heart or lung diseases. Benzo(a)pyrene is known to cause cancer in animals and is believed to be a major factor in lung cancer caused by cigarette smoke. It is found in cigarette smoke and coal tar as well as leaf smoke.  
  
  According to U.S. Environmental Protection Agency studies, sometimes concentrations of air pollutants resulting from leaf burning can be so high that the air does not meet federal health standards. In fact, in some areas burning of leaves and brush sometimes causes much higher levels of air pollution than all other forms of air pollution combined (such as factories, vehicles, and lawn and garden equipment). 
  
  Leaf burning can also reduce visibility, create safety hazards, cause a nuisance, soil buildings and other property, and create additional demands on local police and fire protection. 
  
  See Backyard Burning for more information on the negative impacts of burning yard waste.
  

Getting Started

The following guidance is taken from the Department of Horticulture - Michigan State University Green Tips sheet on Mulching Tree Leaves Into Lawns.

• Leave your mower set to the same height you use to mow your lawn

• Use a rotary mower that pulverizes the leaves

• Mow when the leaves are dry

• Make sure that mower blades are sharp and use a slow movement with the mower to help grind the leaves finer

• 3-4 passes may be required to chop leaves fine enough so that they filter through the turf and expose grass leaves to sunlight; i.e. make sure that pulverized leaves do not cover the grass blades completely

• Ground leaves should settle into the turf in a day or two, especially with rain

• It is best to mow tree leaves regularly, not letting them lie more than 3-4 days

• Although additional nitrogen has not shown any major benefit, the Department of Horticulture - Michigan State University suggests applying 1/2 pound of nitrogen per 1,000 square feet in addition to the normal fall fertilization in order to speed tree leaf decomposition

More Mulching in Place Information:

Below are some links to more information on mulching tree leaves in place.

UW Extension InfoSource
Managing yard waste
Uses for leaves & grass clippings

UW Extension and Wisconsin Department of Natural Resources
Managing Leaves and Yard Trimmings (pdf)

Department of Horticulture - Michigan State University
Mulching Tree Leaves Into Lawns (pdf)
Dealing With Clippings (pdf)