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October 22, 2001

Worrying about falling leaves may be ‘mulch’ ado about nothing

WEST LAFAYETTE, Ind. – If trees dot your yard, every fall you may face the exhausting chore of leaf disposal. Purdue University researchers advise using a lawnmower or shredder to turn the foliage into mulch.

A mulching mower or a mulching attachment will break up the leaves so they can just be left on the lawn. But whether leaves are raked or mulched, thick layers of the colorful foliage must be removed from grass, said Zachary Reicher, associate professor of agronomy and Purdue Extension turfgrass specialist.

"If you don’t get the whole leaves off the top of the grass, you will smother it by preventing photosynthesis," Reicher said. Photosynthesis is the process by which plants convert sunlight to energy for growth and reproduction.

A heavy layer of foliage on the grass not only can kill the grass by blocking sunlight, but it also creates and fosters high humidity that leads to snow mold, Reicher said. "Tree leaves create a perfect environment for this."

Snow mold is characterized by large round or irregular shaped, matted patches in the turf that sometimes have a pinkish color. In severe cases, grass will have to be replaced where the snow mold develops.

"At best, it will thin the turf. At worst, it will kill the turf right down to the ground," Reicher said.

In addition to aiding the lawn’s health, mulching leaves improves soil condition and may provide some added nutrients, although Reicher said this benefit is probably minimal. In Purdue studies of shredding leaves into grass, Reicher and his team found that mulching the foliage didn’t affect the color or quality of grass or have any other negative consequences. Nor did it deplete important turf-sustaining nitrogen.

Mulching is a good alternative to labor-intensive raking, blowing, vacuuming and bagging of leaves, especially since most landfill sites now ban the dumping of lawn clipping and leaves, Reicher said. It is important not to mulch in thick layers of leaves all at once, but instead shred them a little at a time.

"If you try to mulch in six to eight inches of leaves all at once, it’s just not going to work," Reicher said. "And make sure they are dry when you do it; you won’t break them up or get the mower through them if they’re wet."

Aside from saving time and money in removing foliage from the grass, mulching also saves time and money in the spring by keeping grass healthy.

"If you do the right thing in the fall, then you avoid input (of money and time) in the spring," Reicher said.

Writer: Susan A. Steeves, (765) 496-7481, ssteeves@aes.purdue.edu

Source: Zachary Reicher, (765) 494-9737, zreicher@purdue.

Ag Communications: (765) 494-2722; Beth Forbes, bforbes@aes.purdue.edu; http://www.agriculture.purdue.edu/AgComm/public/agnews/

Related Web site:

Purdue Turfgrass Program

Purdue News Service: (765) 494-2096; purduenews@purdue.edu


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