Overseeding With Ryegrass

Prepared by Bob Polomski, Extension Consumer Horticulturist; Bert McCarty, Turf Specialist; and Debbie Shaughnessy, HGIC Information Specialist, Clemson University. (New 06/99.)

HGIC 1206

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Perennial ryegrass (Lolium perenne) and annual ryegrass (Lolium multiflorum) are generally used to overseed dormant warm-season lawns in South Carolina. They provide a green cover during the winter when the warm-season grasses turn brown after frost. Also, they can be used as a winter cover to help prevent erosion on new lawns where the permanent grass has not been established. However, overseeding may retard the warm-season grass unless managed correctly in the spring, because the ryegrass competes for moisture, sunlight and nutrients.

Ryegrass adapts well to either sun or shade. Although cheaper, annual ryegrass is a second choice to perennial ryegrass, since perennial ryegrass has more desirable turf characteristics. Annual ryegrass dies out in late spring after being planted in the fall. Perennial ryegrass usually lives somewhat longer than annual ryegrass, especially in the shade. It can survive for years in some areas of the lawn where it can become a nuisance. It has better disease resistance than annual ryegrass. It is not recommended as a permanent lawn, however, because of its susceptibility to diseases in hot weather. Ryegrasses should only be used in South Carolina for overseeding in the fall.

Seedbed Preparation

It is important to prepare the turfgrass for winter. As temperatures begin to drop in the fall, water demands of turfgrass decrease. Take care not to overwater, as disease problems may increase. Remove any excess thatch so the seed can make good contact with the soil. A heavily thatched lawn tends to result in irregular patches of overseeded grass. Dethatching by verticutting or aerifying will assist overseeding heavily thatched lawns. If core aeration is necessary, overseed thirty days after aeration to allow the holes time to heal and provide an even turf in the winter. Dethatching by verticutting should be performed just prior to overseeding. Mow the lawn closely, catching all clippings or raking afterwards.

Timing

Overseeding should be done when the days are warm enough for the seed to grow and the nights are cool enough to reduce the incidence of disease. Thirty days before the first frost, when daytime highs are near 70 °F and nighttime lows are usually above 50 °F, is generally a good time to overseed. This usually corresponds to mid-September in the Upstate and late September in the Midlands and Coastal regions.

Establishment

Apply 10 pounds of annual ryegrass seed per 1,000 square feet, and 5 to 15 pounds of perennial ryegrass per 1,000 square feet. Use the higher rate if thicker stands of green grass are desired. Sow half the seed in one direction and the other half in a direction perpendicular to the first. This method will help establish a uniform stand of turf. Use fungicide-treated seed to reduce the chances of disease. After seeding, rake the ground with a broom to ensure the seed makes contact with the soil.

Water the lawn lightly two or three times daily until the seeds germinate. Do not overwater, as this will wash seed away and encourage disease development. When the lawn is established, and has been mowed several times, water only as necessary to prevent ryegrass wilt.

Maintenance

An established winter lawn requires the same maintenance as a permanent lawn. Mow when the grass is tall enough to cut, about 1 to 2 inches. Mow to 1 to 1½ inches thereafter whenever the grass reaches 2 to 2½ inches. Make sure the mower blade is sharp to prevent ripping of the ryegrass. If ryegrass is properly fertilized, weekly mowing may be necessary.

After the second mowing, apply one-half pound of nitrogen per 1000 square feet using a complete fertilizer, such as 16-4-8, 10-10-10 or others. Apply a complete, quick-release nitrogen in late winter or early spring. Pythium blight disease can be a problem on overwatered, overfertilized ryegrass, especially during warm, humid weather.

Reestablishment of the Permanent Lawn

Ryegrass normally dies out in late spring, but if cool weather prevails it can become persistent. To discourage the ryegrass, stop fertilization in March. However, do not allow the permanent grass to suffer from lack of water at this time. Mow the ryegrass as close as possible, lowering the mowing height each week. This will weaken the winter grass and allow the permanent grass to rejuvenate. When the permanent grass resumes growth, begin regular maintenance, especially resuming fertilization.

Excerpted from the South Carolina Master Gardener Training Manual (EC 678) and the University of Florida Extension publication Florida Lawn Handbook.

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