In the Garden:
Northern California Coastal & Inland Valleys
September, 2000
Regional Report

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151

Dethatching the lawn with a dethatching rake.

Lawn Renovation

September is the perfect time to renovate your existing lawn. One of the key steps is removing thatch. Each time you mow, the blades of grass fall onto the turf (unless you're bagging your grass clippings, which is a no-no). Over time, those fallen blades of grass build up, creating a layer of thatch that water and nutrients can't penetrate. By removing that layer, by either mechanical or manual means, you open the surface so that air, water, and nutrients can reach the root zone.

Thatch Rakes and Cutters

To remove the thatch layer, you need either a thatching rake or a mechanical vertical cutter. A thatching rake is an ornery-looking hombre that resembles a metal bow rake but has blade-like tines on both sides of the rake head. It's pulled over the turf in the same manner a leaf rake is but goes much deeper into the lawn and cuts through the built-up thatch layer. It's available at garden centers and nursery supply stores and costs about $20.

A vertical cutter is a mowerlike power tool that has vertical blades under a deck that slice into the lawn instead of mowing it down. Vertical cutters can be rented from equipment rental stores.

How to Dethatch

Whichever device you decide to use, keep in mind that thatch should be removed by moving in one direction only. If you go back and forth across the lawn, then in a diagonal direction, you can potentially damage the roots by tearing them from the soil. Removing the built-up layer of thatch should be an annual maintenance chore.

I remove the thatch in a north-south direction in even- numbered years and an east-west direction in odd- numbered years. This method allows me to completely renovate my lawn every two years without damaging the roots.

How Often to Dethatch

You may need to remove thatch more than once in a year if your lawn has a substantial buildup. I have dethatched a bent grass lawn five times in one year to remove the built-up layers. It's a lot of work, but the lawn will look great when you finish. And keep in mind that thatch is a wonderful addition to the compost pile!

Letting the Lawn Breathe

After you have removed the built-up layer of thatch, you may want to aerate. Aeration is the process of introducing oxygen into the soil by punching small holes in the surface. You can either rent a machine called an aerator, use a special hand-aeration tool, or put on a pair of golf or soccer shoes and walk over the lawn.

Aeration Tool

The aeration tool looks like a rake with a bar of round tines across the bottom. You push the aeration rake into the soil by placing your foot on the bar and then pressing down. You can use any tool that will punch holes in the soil and let air get down to the roots. Pitchforks, cultivators, and spading forks all work well.

Sprinkler Check

After removing the thatch, raking away the excess, and depositing it in your compost pile, then aerating the entire surface of the lawn, you still aren't finished. The next step is to check that no underground sprinklers have been damaged in the process. Turn the system on, mark any damaged sprinklers (water coming out too fast or slow), then replace or repair as necessary. Once the sprinklers are in good working order, fertilize with a lawn-specific fertilizer and then water. Although your poor lawn probably looks like it has been through a war, it will recover quickly in the warm fall weather. In a few weeks, if the weather holds, your lawn will be the envy of the neighborhood!


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