Pros and Cons of Overseeding Warm-Season Lawns
There are only a few good reasons for establishing temporary cool-season lawns here in Mississippi. The most important one is to provide some type of groundcover for a new home site where it is too late in the fall to establish a permanent lawn. The temporary lawn would prevent erosion problems, prevent tracking mud into the home, etc. A logical reason may be that you have had your permanent lawn damaged in some way and it will be vulnerable to additional winter injury if not overseeded. Another may be that you will be having some special event such as an outdoor wedding or family reunion that simply requires that the lawn be perfect at that time. And lastly, although somewhat a questionable good reason is that you simply must have a green lawn all year.
In reality overseeding your permanent warm season lawn with cool season grasses will delay next springs green-up of the permanent lawn and may actually weaken it. Just keep in mind that cool season turf species thrive at temperatures in the 60-70 degree range, so next spring when your permanent lawns begins to break dormancy, the over seeded turf species will be very competitive and act similar to any other weeds competing for nutrients, water, and space.
The turf species of preference for winter overseeding warm season lawns should be perennial ryegrass. Perennial ryegrasses are much finer textured than annual ryegrass cultivars, generally have much better color throughout the winter, not as prone to clumpiness, and do not produce as many unsightly seed stalks in the spring. Seeding rate for home lawns with perennial ryegrass should be 8-10 pounds per thousand square feet and if you use annual ryegrass increase this by another 2 pounds. Seeding should be done when soil temperatures reach around 70 degrees, which, as a general rule, will occur around the middle of October for much of Mississippi.
Cultural practices of mowing, fertilizing, watering, and pest management must be continued throughout the winter for an over seeded lawn. There are labeled herbicides available now that are very effective in removing cool season turf species from warm season permanent lawns so you may want to consider using one of these in the spring to remove the ryegrass once the permanent lawn begins spring growth.
Published October 3, 2011
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. firstname.lastname@example.org