Published on 02/26/96

Dethatching Lawn Important, but Wait Until Summer

The long, hard winter has made life so tough for your lawn that a normal, helpful practice may not be such a good idea now.

Normally, late-winter dethatching of dormant turf is a good idea. But normal winters aren't as harsh as the one your lawn has just endured.

"We had some pretty cold weather this winter," said Gil Landry, a turf specialist with the University of Georgia Extension Service. "Because of that, you might want to hold off on your normal dethatching while your grass is still dormant.

"It would be safer to wait until after the turf greens up and is growing well," he said, "but before the hot, dry weather of July and August."

Be sure to keep the root zone moist during spring green-up, too, Landry said.

"Apply at least one-quarter inch per week until 50 percent green-up, and then go up to one-half inch per week," he said. "Water at this time can literally save your grass.

"Just like you," he said, "our grass needs water to be healthy. A little water now can get your grass off to a good start for the rest of the season."

Dethatching is still important for your lawn, though. Thatch is a buildup of dead grass stems and other plant matter between the grass and the soil.

If thatch gets more than a half-inch thick, you need to do something about it.

"If it gets that thick," Landry said, "most of the grass root system is growing in the thatch, not in the soil."

That can lead to all kinds of problems for the lawn. Thatch freezes faster than the soil. That can make winterkill worse when hard freezes come.

Thatch dries out faster than soil, too, so the lawn will be stressed more by summer drought stretches.

"Thatch is also a good environment for insects and disease organisms that can injure the grass," Landry said.

You may have a thatch problem, he said, "particularly if you have centipede grass, if the lawn is really spongy and soft when you walk across it."

Dig your fingers into the sod, grip the grass and try to move it around. If the grass moves, you have too much thatch. "You shouldn't be able to move it at all," he said.

How do you get rid of thatch?

Most people use a vertical mower or some attachment to a lawn mower. You probably don't have a vertical mower, but most towns have rental places that carry them.

"On centipede or St. Augustine, the vertical mower blades need to be two to three inches apart," Landry said. "Blades closer than that would remove too much turf and increase the recovery time for the grass. And you should go across the lawn only one time.

"With Bermuda or zoysia grass the blades can be closer together," he said. "And you can go across the lawn more than once."

Don't try to get rid of all that thatch at once.

"Do it gradually," Landry said, "to prevent too much damage to the turf."

The best way to handle a thatch problem, though, is to prevent it.

"You can do that by mowing your grass at the proper height," Landry said. "Mow it often enough that you remove only a third of the total height."

You get a bonus if you mow the grass on a good schedule, he said.

Besides keeping thatch from building up, you don't have to remove grass clippings. And that allows you to recycle your costly fertilizer all summer.

Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.