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Lawn Thatch Problem: Lawn Aeration OR Dethatching?

August 7, 2017

First let’s talk about thatch.  When a lawn has more than a half inch of thatch; water, air and nutrients may not be getting down to the roots. The tell-tale sign to look for is if your lawn does not really turn a healthy green after feeding. You can check your thatch layer thickness by removing a plug of grass, soil and all, and measuring the brown thatch layer between the green growth and soil layer. If thatch is greater than a half inch, consider aeration or dethatching.

This illustration shows that root depth is restricted by both compacted soil (far left) and too much thatch (2nd from left). Feed your lawn after aerating. The result is improved root growth as shown in the far right illustration.

I recommend Lawn Aeration using a machine that removes cores from your lawn in cases where you want to improve your existing lawn by opening up the thatch layer without tearing it up.  A dethatching machine may be a better choice if you are trying to remove dead thatch to expose soil so new grass seeds have a better chance of getting started.

Since fall is a great time to aerate cool-season grasses, this is a very timely topic for those with bluegrass, ryegrass, fescue and bentgrass. The best time to aerate warm-season grasses is early summer, however if you have a severe thatch problem in your Bermuda, Zoysia or St. Augustinegrass you can aerate anytime your lawn is actively growing.

A second reason to aerate a lawn is if the soil is compacted. You can tell if your soil is compacted if it is difficult to stick a screwdriver into your soil even when it is wet. When a lawn gets a lot of use (like you get with athletic fields or golf courses) the soil can get packed down and compacted, restricting the flow of water and nutrients. There are some tell-tale signs that your lawn may be compacted. Poor drainage is one. If water pools up on your lawn or runs off instead of soaking in, it could be because the soil is compacted. Lawns that look worn-out are often because of compacted soil.

Aerate your lawn by making individual holes around three quarters of an inch in diameter, three inches deep, and no more than 3 inches apart. This is best done with an aerating machine that removes plugs of soil, NOT the kind that just punches spike holes in the lawn. Soil should be moist enough for the machine to remove plugs that are around 3 inches long. Follow up the aeration with a feeding of Scotts Turf Builder or Scotts Natural Lawn Food.

You can rent an aeration machine at many Home Centers and Hardware stores.

Oh, here’s some good news: after aerating, you can leave the plugs on your lawn.

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2 Comments
  1. Joyce permalink

    Hi Ashton,
    I live in Southside, VA. Last Fall I over-seeded my lawn using a Fescue blend. The grass was looking good earlier in the Spring but then as the humidity picked up, it developed Brown Patch. I had the grass sprayed with a Fungicide. Just about the time it started responding to the treatment, we had 3 weeks of no rain and extremely hot temperatures. Needless to say, now my lawn is in bad shape. My question to you…..do I need to spray a Fungicide again before over-seeding in September, or will a good aeration do the trick?

    • Hi Joyce
      Sorry about your lawn problems. You may get by without another fungicide treatment prior to seeding as weather conditions may be less favorable for Brown Patch. Be sure to do most of your feeding in fall… Up to 3 feedings are recommended. Too much spring feeding encourages Brown Patch in your neck of the woods. In the future if you have this fungus you may find that Scotts Lawn Fungus Control granular will work for you as it is systemic (gets absorbed into the grass). Also if you are irrigating, morning is best. Good luck.

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