Dethatching 101: All About Lawn Thatch

You’ve finally decided to take action to fix your lawn this year. But you’re wondering if it needs dethatching. What is thatch anyway, and is it a problem?

Thatch is the build-up of old grass roots and organic debris where the grass stems meet the soil. The photo below shows a layer of thatch measuring just over 1 inch. (Image adapted from the University of Maryland Extension ). Healthy lawns can have a thin layer of thatch (less than ½” thick) and still thrive. However, excess thatch gets in the way of water and nutrients reaching the soil and feeding the roots.


How do you know if you have too much thatch? To measure the thickness, first, find the brown layer just below the grass blades. With your finger or a stick, poke a hole through this layer to the top of the soil. Measure this brown layer which is the thatch.

With adjustments to your lawn care maintenance, you can resolve your thatch problem.

Thatch is:

1) A result of grass roots growing across the surface of the soil, layering on top of each other, and building up over time; and

2) Dead organic debris that is not being consumed by the soil microbes.

Let’s address grass roots first. In the PNW, our primary grass seed mixes are ryes and fescues. Ryes and fescues are clumping grasses that have the ability, if allowed, to grow roots as deep as 14 feet! If your ryes and fescues are growing across the upper soil layer, it’s an indication the soil is too compact, preventing the roots from growing downward.

The other grass seed that could be blended with ryes and fescues is Kentucky Bluegrass. Kentucky Bluegrass has shallow roots and is “rhizomatic” meaning it grows left-to-right and not downward like the clumping grasses of the ryes and fescues. But, if Kentucky Bluegrass is mixed in, it is a tiny percentage of the seed mix, usually not exceeding 15%. The point is, if you have thatch, it is probably not the Kentucky Bluegrass that is causing the build-up.

Thatch is also composed of dead organic matter that accumulates because it is not broken down. This is a sign that your soil microbial activity is low. Healthy soils can contain more than 4 billion microbes in a single teaspoon. If you have healthy microbes, they will continually consume the dead organic matter and make it into food available for your lawn to consume. This is why we recommend mulch mowing, giving back this valuable food to the microbes, returns up to a quarter of the nitrogen needed for your turf.

What to do if you have thatch build-up?


A gas-powered dethatcher is the first step of the solution. Excess thatch is then raked away and composted. Since dethatching can be hard on your lawn, it’s best to reseed afterward. To prevent thatch from returning, the lawn should be aerated annually and a blend of soil microbes added. Be sure to feed these microbes some organic compost, and when you mow, the mulched lawn clippings. Infusing your lawn with a high-quality compost tea will boost the microbial life in your soil. We brew a probiotic compost tea, FertileTea, for our customers' lawns and apply it with premium organic fertilizers. Keep your soil microbes alive and well by omitting herbicides, insecticides, and synthetic fertilizers on your lawn.

Following these basic steps will get your lawn back on the path to being healthy. A good organic program can help prevent thatch by replenishing the soil microbes and encouraging grass roots to grow deeper. As an added bonus, you can reduce your watering and fertilizing.

Want to learn more about Lawn Dethatching? Give us a call. We’d love to help.

Earthdance Organics | (253) 927-2523 |