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When Should I Dethatch My Lawn?

Lawn Basics
4 min read

For healthy, lush lawn growth, learn why, when, and how to dethatch your lawn from the knowledgeable experts at Jonathan Green.

Jonathan Green supplies genetically superior cool season grass seed, soil enhancers, fertilizer, and organic lawn products to professional customers, such as sod growers and independent hardware stores and garden centers throughout the Northeast, Mid-Atlantic, Midwestern United States, and recently the far Western United States.

What is Thatch?

Thatch is a layer of organic matter that consists of living and dead stems, shoots, and grass roots. It is a symptom of a lack of adequate microbial activity in the soil that is most often caused by acidic soils (pH 5.5 or lower), poor soil aeration and drainage, and improper watering methods.

A small amount of thatch can be healthy, say up to 1/2 inch, and provide insulation against temperature extremes and fluctuations in soil moisture.

Excessive thatch, however, can become a breeding place for insects and lawn diseases and fungus. It can reduce the lawn’s tolerance to cold, drought, and heat stress; rob the soil of its ability to absorb water, oxygen, and nutrients efficiently; and prevent grass roots from pushing deep into the soil.

When to Dethatch Your Lawn

Before dethatching your lawn, first take a garden trowel or spade, dig up a small plug of lawn grass and soil, and measure the layer of thatch between the top growth and the root zone.  If it exceeds a healthy 1/2″ in depth, you should dethatch the lawn.

Dethatching should be done when your lawn is in its peak growing period. For cool season grasses, such as Black Beauty® turf grasses, this will be during the late summer or early fall. The lawn will recover more quickly when the grass is actively growing. For warm-season grasses, dethatch in late spring. Never dethatch a lawn that is dormant or stressed or you may damage it and have to reseed it to ensure its recovery..

How to Dethatch Your Lawn

If your lawn is small, you can dethatch it with a special thatching rake. This is heavy metal rake with sharp tines that slice into the thatch. (Leaf rakes can be used but may not work as well.)  Dig deep to penetrate the thatch and loosen it.

For larger lawns, you may prefer to rent a power dethatcher from your local garden center or equipment rental center. Similar in appearance to a large, heavy gas mower, the power dethatcher has knifelike blades that slice into the turf vertically. Make several crisscrossing passes to cut and loosen the thatch.

What to Do After Dethatching

After dethatching the lawn, use a leaf rake to rake up and remove the debris. Then water the lawn.

This is a good time to aerate your lawn. Aeration will create openings in the surface of the lawn that help water, air, and nutrients better penetrate the soil. This helps alleviate soil compaction, creates better air flow around the roots of the grass plants, and encourages the roots to grow more deeply.

To prevent future thatch problems, consider adding humate-rich, gypsum-based amendments to the soil. Jonathan Green MAG-I-CAL® Plus is a natural, humate-rich, three-in-one “soil food” that loosens hard soil, stimulates soil microbes, and adjusts soil pH. MAG-I-CAL® Plus is available for acidic soil and alkaline soil and should be used every season to keep your soil biology and chemistry balanced. It breaks up clay and compacted soil for better air, water, nutrient, and root penetration.

Visit Jonathan Green online or your nearest independent home and garden store for more information on when and how you should dethatch your lawn to reinvigorate it and keep it looking its best.

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