Many types of lawn grass suffer from sever accumulations of thatch that are both unsightly and unhealthy for the lawn. Thatch that is thicker than 1/2 inch creates favorable conditions for pests and diseases to harm your grass. The most effective method to mechanically remove the thatch is to use a power rake, also called vertical mower.
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You can rent a power rake from your local rental store. These machines are as simple to run as ordinary lawn mowers, and it is cheaper to rent the machine than to pay someone else to do the dethatching. If you don't have access to a power rake, you can buy an attachment that mounts in place of your blade on the lawnmower, but they are not very effective, according to University of Minnesota Extension horticulturists.
Set the height of the unit so the blades or tines of the rake just barely scrape the dirt of your lawn. If the blades rake too deeply, they will wear out quickly, and if they are set to high, you will not get a proper raking. Make sure the unit is not running when adjusting the height.
With the unit running, begin moving slowly back and forth across your lawn, ensuring you are covering the whole area. When done properly, the power rake should be pulling up quite a bit of dead grass. It is normal that some live grass will be pulled up also.
The best times to power rake your lawn is between late August and early October. If you cannot detatch the lawn at this time, early spring is another favorable period.
Once you have fully raked your lawn, you can either dispose of the dead grass or use it for composting.