Released July 9, 2009
MANHATTAN, Kan. – Out-of-town business and summer vacations both can conspire to keep lawn owners from maintaining the mowing practices recommended for fescue and bluegrass health. The results can be long-lasting.
“If you’re about to leave town for awhile, you should resist the temptation to mow these cool-season turfs much shorter than usual. When you return, you should practice patience and gradually return a too-tall lawn to its recommended height. Ignoring either practice could easily lead to your having to overseed or replant this fall,” said Ward Upham, horticulturist with Kansas State University Research and Extension.
During hot weather, an abrupt change to a much shorter mowing height can seriously diminish cool-season turfs’ root growth, he explained. As a result, the “scalped” plants crave excessive watering. And, if they don’t get it, the outcome is likely to be a thinner, weaker lawn with more room for weeds.
“If you rank Kansas’ common turf grasses on their tolerance for short mowing, tall fescue is the least tolerant. Kentucky bluegrass is next in line,” Upham said. “Besides, these turfs ‘fight back’ if you cut off more than a third of their grass blades’ height at one time. They quickly send up new growth, drawing on what’s left of their stored energy reserves … and, defeating your purpose.”
Allowing cool-season turfs to grow too tall can greatly erode lawn quality, he warned. They can become coarse and stemmy and may lodge (fall over). Because it’s a bunch grass, tall fescue may also get clumpy.
“You can compound the situation by mowing off more than a third of an overgrown lawn,” Upham said. “If your mower won’t adjust that high, though, just set it as high as you can. Then bring the turf’s height down slowly by cutting often and at progressively lower mower settings until you reach target height.”
K-State recommends keeping tall fescue mowed 3.5 to 4.5 inches tall. So, given the one-third rule, the deadline for getting out the mower is whenever a fescue lawn reaches 3.75 to 5.25 inches high. The recommendations are the same for Kentucky bluegrass, except 0.5 inch shorter overall.
More information about mowing for turf health is at http://www.oznet.ksu.edu/library/hort2/MF1155.pdf.
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http://www.oznet.ksu.edu/ksrenews/story/briefs070909.aspx
Contact: Elaine Edwards, elainee@ksu.edu
