Friday, November 20, 2009 3:08 PM CST
Yard and Garden: Forget the rake -- mulch those leaves!
By Jon Collins, Master Gardener
Several weeks ago Herb Meeker, staff writer for the Journal Gazette/Times-Courier, wrote a tongue-in-cheek editorial about leaf removal problems in Mattoon. It contained a lot of noise and commotion with leaf blowers blasting; hand rakes flying; bags being stuffed; and even a beeping mini-backhoe moving huge piles of leaves into the street.
I have a comment to add to all this blowing, raking and stuffing. Don’t do it!
In my estimation, there are only two reasons to move leaves about on a lawn. The first would be, you want to use the leaves for mulch. Pine needles and bald cypress leaves make a good, loose mulch. So a little raking and transporting is understandable.
The second, the grandkids are coming for the weekend. Raking piles, then stomping on, jumping in, diving under and rolling over leaf piles should to be a highlight of fall outdoor activities for kids.
But back to Herb’s article. He did say after all his own raking and bagging, that he “might even try mulching some of the leaves on my lawn with my mower.”
Yes. He has hit on a solution that makes sense. This is a solution that many professional grounds managers have been using for years. And I can personally confirm that this is the practice on the grounds at Eastern Illinois University and also at Morton Park in Charleston.
Mulching leaves with a rotary mower and leaving the pulverized leaves in the lawn to decompose is the sensible and economical way to dispose of fallen leaves.
This economical choice is backed up by some extensive research at Michigan State University. Since 1990 MSU’s Hancock Turfgrass Research Center has conducted three studies to examine the feasibility of mulching tree leaves into existing turf grass canopies. What follows are excerpts from a summary of those studies compiled by Thomas A. Nikolai, academic turfgrass specialist at MSU.
The first study, beginning in 1990, examined mulching deciduous leaf rates of 50 and 100 pounds of dry leaves per 1,000 square feet (3-inch and 6-inch layers) and the timing of nitrogen fertility applications.
“The objectives were to determine if there were any negative effects of mulching tree leaves into the existing canopy with a lawn mower and if the nitrogen fertility would enhance leaf-litter decomposition. The study ended in 1996, concluding that there were no negative effects at the rates applied and that the nitrogen treatments did not aid in the degradation of leaf litter.”
“The second study was initiated in October 1991 to examine the effects of mulching different leaf types (oak and maple) at the rate of 100 pounds of dry leaves per 1,000 square feet (6-inch layer) into bluegrass turf using a rotary push mower. The objectives were to determine if different leaf types would have an effect on soil pH or turfgrass quality.
“The study concluded in the fall of 1998 with the following conclusions. Turfgrass quality increased on plots that had maple leaf treatments due to the fact that less broadleaf weed growth was observed in those plots. No differences were observed regarding soil pH for the duration of the field experiment.
“Soil cores taken in the fall of 1998 concluded that there was an increase in the amount of organic matter in plots that had oak and maple leaves mulched into them compared to the check plot.
“These studies led to the conclusion that there were more benefits than negatives for turf managers and homeowners who mulch tree leaves into existing sites.
“With these facts in mind, the third leaf-mulching study was initiated in October of 1995. The objective was to determine if low-maintenance turf grass sites could take heavy loads of deciduous leaves and maintain their usefulness. The study consisted of mulching a mix of deciduous leaves into an existing sunny mixed-turf area.
“Excessive leaf rates of 150, 300 and 450 pounds per 1,000 square feet (approximately 6-inch, 12-inch and 18-inch layers) were mulched in with the aid of a mulching mower. Two mower deck heights (1.5 and 3 inches) were included in the study to determine if deck height had a significant impact on the degradation of the leaf litter.
“Mulching at such excessive rates resulted in visible leaf litter still being present in the spring. As anticipated, as the rate of leaves mulched increase, the percentage of visible leaf litter increased. However, at the higher mower-deck leaf-mulching height of 3 inches, there was reduced visibility of the leaf litter the following spring.
“This is most apparent at the dry leaf rate of 300 pounds per 1,000 square feet. It is noteworthy that all visible leaf litter soon dissipated as the grass growth increased in the spring, and these plots also tended to green-up quicker.
“Research clearly indicates that the practice of mulching leaf litter into existing turf grass canopies provides benefits for the soil and the turf grass plant.”
For best results on your own lawn, leave the mover set at the same height as you have been mowing the turf. It is important to use a rotary mower that pulverizes the leaves well and that the leaves are dry when mowed. A mulching mower works best, or a normal mower with a covering over the discharge opening (usually standard with most mowers sold today) works well also.
Sharpening the mower blades and a slow movement with the mower will help to grind the leaves finer. It may be necessary to make as many as three or four passes over the area to grind the leaves fine enough, especially if you haven’t been mowing regularly. It is best if the leaves are mowed regularly, not allowing them to lie on the turf more than three or four days.
The pulverized leaves will settle into the turf within a day or two, particularly if followed by rain. Take care that the pulverized leaves do not cover the grass blades entirely. Fall is a very important time for the turf to photosynthesize and store carbohydrates.
I realize that most of the leaf removal season is over for this year, but next year, forget the rake. Just keep on mowing.
If you have any horticulture questions, call the local University of Illinois Extension office Monday through Friday at 345-7034. Volunteer Master Gardeners are not in the office this time of year; they will return your call. This column is based on information and materials at the U of I Extension office, located at 707 Windsor Road, Suite A, Charleston, 61920; phone 345-7034; or Web site: www.extension.uiuc.edu/coles/.
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arrass wrote on Nov 22, 2009 8:31 AM:
These blades are available for many riders and push mowers. "