Can You Dethatch & Overseed in the Summer?

Problems with Summer Dethatching and Overseeding

• Its important for gardeners to dethach and overseed when temperatures are not too hot or the ground too dry for proper seed germination. Grass seeds have difficulty germinating when the soil is dried out; therefore, gardeners must apply water several times a day to prevent their seeds from drying out. Also, overseeding must be performed immediately after dethatching. Dethatching causes bare spots or areas where the grass was unable to spread due to the thick layer of thatch. Leaving those bare areas in the lawn gives weeds the perfect opportunity to invade.

Cool-Season and Warm-Season Grass Types

• Cool-season grass types such as bluegrasses, fescues, bentgrasses and ryegrasses start growing in the early spring. Meanwhile, warm-season grass varieties like Bermuda, zoysia, St. Augustine and centipede grow in late spring. It is important for gardeners to overseed their lawns with grass seeds when soil temperatures favor proper germination. Germination temperatures differ depending on the grass type. For example, Kentucky bluegrass germinates when temperatures are between 59 to 85 degrees F, sheep fescue germinates when temperatures are between 59 to 77 degrees F and Bermuda grass needs the soil to be above 65 degrees to germinate. Check the soil temperature with a soil thermometer before dethatching and overseeding.

When to Dethatch

• Gardeners dethatch their lawns when the thatch layer exceeds 1/2 inch. Thatch is the natural accumulation of organic matter between the grass and soil. When the thatch layer is too thick, lawns have difficulty spreading, growing strong root systems, overcoming diseases, absorbing fertilizer and receiving water. By checking your thatch layer and dethatching at the beginning of your grass' growing season, you prevent numerous problems throughout the year.

Dethaching and Overseeding

• Cut a 2-inch wedge of turf out of the lawn with a trowel. Measure the brown spongy thatch material between grass and soil. If the layer is over 1/2 inch, dethatch the yard. Water your lawn for a couple of days before dethatching and mow the grass. Use a power dethatcher, which can be rented at garden supply stores or rental centers, to remove your thatch layer. Water the bare areas in the lawn and distribute your grass seeds in bare or thinning places. Keep your seeds moist until your seedlings grow to 3 inches.