Local lawns and landscape plantings have taken a beating from the hot, dry conditions this summer. It may be hard to imagine now, but the best time of year for lawn renovation is right around the corner. Most lawns in need are choking in weeds and debris and/or suffering from soil compaction. Dealing with these two problems first will begin the rehabilitation of your lawn.

THATCH
Thatch is the dead layer of plant debris on the soil surface and it can cause major problems. A thin layer of thatch can help retain soil moisture and protect the roots from extreme heat. But a thick layer of thatch not only prevents water from reaching the roots but can also harbor insects and disease. By obstructing the light from reaching the roots, the turf is not allowed to spread as it would otherwise. Thatch more than 1/2 inch thick should be removed.

Thatch can be removed in small areas by raking with a thatch rake, a double sided heavy rake with crescent shaped blades that cut through and pull up thatch. If your lawn is large, a gasoline powered dethatcher, also called a verticutter will make easier, more thorough progress. Sharp vertical blades slice through the thatch and lift it to the surface where you can take it away.

Thatch can consist of grass plant debris as well as weeds such as crabgrass, so removing thatch is the first step toward rejuvenating your lawn.

COMPACTED SOIL
Compacted soil robs grass plants of water and oxygen and can cause thatch to build up. A core cultivator or aerator pounds the earth with hollow tubes that extract thin plugs of soil a few inches long. The extracted plugs can be composted or pulverized with a rake and left on the lawn.

After aerating the soil, it can be further improved with the addition of a layer of topsoil, sand or compost. This material will seep into the holes and improve the tilth and drainage. A top dressing of organic material will increase the number of microorganisms and earthworms in the soil, both of which aid in reducing thatch. Spread about 1/2 cubic yard per 1000 square feet of lawn. The best time to apply this top dressing is in the fall.

RESEEDING
If thatch or soil compaction isn’t a problem, a weedy, thin lawn can be restored with regular maintenance and reseeding. If the area drains well and the percentage of weeds is less than 25%, try reseeding. Most new grasses are so vigorous that they will eventually crowd out older, weaker strains of grass in the lawn. But the new seed must get off to a good start, so sow in the fall or early spring.

Before you sow, mow the grass closely to half the normal height, as close as 1/2 inch, depending on the species of grass. Rake thoroughly and vigorously. Remove all the grass clippings and as much thatch as you can. Expose and rough up as much soil as possible and pull up all the weeds you find. A verticutter for large lawns will make this step faster and more thorough.

Since you are not sowing the seed into bare ground, seed five to eight pounds of seed per 1000 square feet of soil. Then rake the entire area lightly and top dress with a thin layer of peat or topsoil. Water the area thoroughly with at least an inch of water. Keep well watered and stay off until the grass has come up. Don’t mow until it has reached its maximum mowing height (2-4 inches).

Fine Fescues, Kentucky bluegrass, tall fescue and turf-type perennial ryegrass are the predominant cool weather grasses that thrive in this part of the country. The highest quality lawns are normally a combination of improved cultivars.

HEAT TIPS
Small trees and shrubs are very prone to damage from the heat. Deep watering (1 inch a week) will make the life and death difference.

Keep deadheading annual flowers for continuous bloom. Winners this season of the “Beat the Heat” award: Orange Cosmos (golddfinches love the seed), Datura, a tropical spreading plant covered with fragrant white flowers that open in the evening, and all types of Cannas. Plants that are water dependent and sensitive to the extreme heat include Impatiens and Lavatera. Try to water more thoroughly less often to avoid disease in these species.

Cut back leaves on spent perennials such as iris, lilies and gladiolus. Make room in flowerbeds for mums and ornamental kale and cabbage.

Robin Milliken is a Landscape Specialist and Master Gardener
The Master Gardener appears monthly in The Olathe Daily News.
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