Thatch control for cool-season lawn grasses such as 
bluegrass and tall fescue is usually done in the fall but now is the 
time we should perform this operation for warm-season turfgrasses such 
as bermudagrass and zoysiagrass. Because these operations thin the lawn, 
they should be performed when the lawn is in the best position to 
recover. For warm-season grasses that time is June through July. 
Buffalograss, our other common warm-season grass, normally does not need 
to be dethatched.

When thatch is less than one-half inch thick, there is 
little cause for concern; on the contrary, it may provide some 
protection to the crown (growing point) of the turfgrass. However, when 
thatch exceeds one-half inch in thickness, the lawn may start to 
deteriorate. Thatch is best kept in check by power-raking and/or 
core-aerating. If thatch is more than 3/4 inch thick, the lawn should be 
power-raked. Set the blades just deep enough to pull out the thatch. The 
lawn can be severely damaged by power-raking too deeply. In some cases, 
it may be easier to use a sod cutter to remove the existing sod and 
start over with seed, sprigs or plugs.

If thatch is between one-half and a 3/4- inch, thick, 
core-aeration is a better choice. The soil-moisture level is important 
to do a good job of core-aerating. It should be neither too wet nor too 
dry, and the soil should crumble fairly easily when worked between your 
fingers. Go over the lawn enough times so that the aeration holes are 
about 2 inches apart.

Excessive thatch accumulation can be prevented by not 
over-fertilizing with nitrogen. Frequent, light watering also encourages 
thatch. Water only when needed, and attempt to wet the entire root zone 
of the turf with each irrigation.

Finally, where thatch is excessive, control should be 
viewed as a long-term, integrated process (i.e., to include proper 
mowing, watering, and fertilizing) rather than a one-shot cure. One 
power-raking or core-aeration will seldom solve the problem.

Alicia Boor is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact her by e-mail at [email protected] or calling 620-793-1910.