Grass seed sprouts best when the soil is constantly moist, such as in rainy seasons, and when the soil temperature is right for the grass variety. Warm-season grasses thrive in summer in warm U.S. Department of Agriculture plant hardiness zones but turn brown and become dormant over winter. Cool-season grasses grow well in the moderate temperatures of winter in warm USDA zones and spring and fall in cool and cold areas of the United States.
Late summer or early fall are the best times for reseeding cool-season grasses. Tall fescue (Festuca arundinacea) and Kentucky bluegrass (Poa pratensis) are two cool-season grasses that can be used to reseed lawns in cool and cold USDA zones. Tall fescue is hardy in USDA zones 4 through 7, and Kentucky bluegrass is hardy in USDA zones 2 through 6.
Both grasses sprout and grow well in spring or fall, but in spring they and other cool-season grasses must compete with lawn weeds, and when summer arrives, the young plants are stressed by heat and drought. Fall-sowing allows cool-season grasses to establish before winter. Sow cool-season grasses six weeks to two months before the first local average frost date in USDA zones 7 and colder. Both grasses have invasive tendencies.
A Warm-Season Lawn
Reseeding a warm-season lawn with cool-season grasses provides a green lawn over winter, when the warm-season grasses are dormant. Perennial ryegrass (Lolium perenne) and annual ryegrass (Lolium multiflorum) grow well in winter in warm USDA zones, and they are often sown over Bermuda grass (Cynodon spp.) and zoysia grass (Zoysia spp.), which turn brown. Perennial ryegrass is hardy in USDA zones 3 through 6, Bermuda grass is hardy in USDA zones 7 through 10, and zoysia grass is hardy in USDA zones 5 through 10.
Fall is the best time for reseeding with cool-season grasses on a warm-season lawn, when the daytime temperatures are lower than 85 degrees Fahrenheit. All the grasses have a tendency to become invasive.
A thin warm-season lawn benefits from reseeding with warm-season grasses midspring through midsummer. Bermuda grass, zoysia grass and other warm-season grasses need warm temperatures to sprout. Sow warm-season grasses when the soil temperature is between 65 and 75 degrees Fahrenheit.
- Mow the lawn at the lowest setting on your lawn
mower before reseeding a lawn, and rake up the grass
- Run a dethatcher over the lawn if the thatch layer is thicker than 1/3
inch. Thatch is a layer of moss, driedlawn clipping and plant debris. Remove 50 percent of the thatch.
- Remove plugs of soil with a lawn aerator to help break up soil compaction.
- Divide the seed into two portions and put one portion in a hand, drop or broadcast spreader. Make one pass over the lawn up and down or side to side, and spread the second portion of seed in the opposite direction.