Growing in hot summer temperatures and tolerant of foot traffic, perennial Bermuda grass (Cynodon dactylon) is green from spring to fall but goes brown and dormant in winter. It's hardy in U.S. Department of Agriculture plant hardiness zones 6 through 9. Restore a green winter lawn by overseeding Bermuda grass with rye grasses (Lolium spp.), which grow well in cool weather.
Annual Rye Grass
Two kinds of rye grass are available for overseeding. Annual rye grass (Lolium multiflorum) is hardy to USDA zones 4 through 8, but it grows as an annual almost anywhere. It dies naturally at the end of winter. It presents a rather coarse texture and is light green.
Perennial Rye Grass
Perennial rye grass (Lolium perenne, USDA zones 5 through 7) grows as an annual in mild winter climates. It can't withstand high temperatures and dies in hot summers. In cooler summer areas, it may linger on and pose a problem to the permanent turfgrass. Perennial ryegrass is darker green and finer textured than annual ryegrass but is more expensive.
Timing the Job
Rye grass needs enough warm weather to germinate well and to start vigorous growth before winter's cold sets in. A general guideline is to reseed 30 days before the first frost, with daytime high temperatures around 70 degrees Fahrenheit and nighttime lows are above 50 degrees F. This will vary by geography, however.
Geographical Area Variations
In desert areas of Arizona, for instance, the University of Arizona Extension recommends reseeding around Oct. 1, when temperatures can still be in the 90s and the first frost is usually in late November. In Mississippi, Mississippi State University Extension reseeding time goes from Oct. 20 to the end of November. In North Carolina, Clemson University Extension identifies reseeding time in the upstate region around mid-September and for the midland and coastal areas, late September.
Before sowing rye grass seed, cut back the existing Bermuda grass close to ground level. Remove all the grass clippings, either in a mower grass catcher or by raking it up. You may have to dethatch the lawn. If that's needed, do it 30 days in advance of seeding. The rye seed has to be able to contact the soil between the stems of existing lawn grass.
To apply rye grass seed, broadcast the seed evenly by hand or use a lawn seeder. Overlap the areas of seed application to get even coverage. Sow seeds at the rate of 1 to 1 1/2 pounds of seed per 1,000 square feet. Cover the seeded area with a thin layer of organic mulch such as aged manure or aged compost. This helps keep the seeds moist between waterings and helps hide the seeds from hungry birds.
Water the seeded area lightly several times a day, especially during hottest times. The seeds need to be kept moist at all times for germination to occur. If the seeds dry out, they die. Ordinarily, annual rye germinates in about seven days. After the seeds germinate and you can see new green growth throughout the area, space watering every day or every other day, depending on the weather.
Rye Grass Care
You can mow the new grass when it's about 2 to 3 inches tall, removing the clippings from the first mowing. Thereafter, mow the grass at about 1 1/2 to 2 inches above the ground when grass is 1 inch above that level. Fertilize after the second mowing, applying about 1/2 pound of nitrogen per 1,000 square feet of granular 16-4-8. Reapply the fertilizer in late winter or early spring. Water the grass sufficiently to keep it from wilting. Excess moisture can encourage development of fungus disease.
Stop fertilizing in March to discourage rye grass growth into the time the Bermuda grass starts growing again. When nighttime lows begin to reach 60 degrees Fahrenheit, usually in late spring or early summer, again cut back the lawn close to ground level. Although the rye grass normally dies back with the arrival of summer heat in mild winter areas, this gets it out of the way so the Bermuda grass gets good light.