Overgrown Lawn? What to Do, What to Do

Manhattan, Kansas (June 3, 2010)--Summer vacations and rainy weather both can make sticking to the "One-Third Rule" for mowing tall fescue and Kentucky bluegrass lawns a practical impossibility.

"The per-mowing limit on reducing lawn height is important. If you cut off more, the plants will respond as if their food-making ability is under attack. They´ll use their stored energy reserves to quickly send up new growth," said Ward Upham, horticulturist with Kansas State University Research and Extension.

The source, rather than the speed of this response is the real problem, Upham said. The plants end up with less stored energy available, in case they need it to deal with future weather stress, insects or disease.

Unfortunately, mowers can´t always be adjusted as high as they need to be, to remove no more than a third of an overgrown lawn´s height.

"In that case, the best thing to do is to set your mower as high as possible and get it going. If the clippings are too long to filter down into the lawn, you´ll need to bag or rake them up, too," Upham said. "Then, gradually bring the lawn´s height down -- cutting more often than usual and progressively lowering your mower as you do -- until you reach the turf´s target height."

Although Kentucky bluegrass can be a bit shorter and tall fescue a bit taller, K-State recommends mowing both turfs about 3 inches high.

They´ll be ready for another mowing when they reach 4.5 inches - one- third of which will be the 1.5 inches the mower removes to get the lawn back to 3 inches tall.

"You can´t think of this as something like straightening the house or getting a haircut," Upham said. "How it´s mowed has a huge impact on a lawn´s density, vigor, root system, water use, weed pressure and resistance to stress."

More information about mowing all of Kansas´ major lawn turfs is available on the Web at www.ksre.ksu.edu/library/hort2/MF1155.pdf.