Reseeding Lawns in Summer

The Struggles of Summer Seeding

• Summer brings a variety of soil and weather conditions that make reseeding more troublesome. Most common lawn grasses are cool-season species, meaning they thrive only during the mild temperatures of spring and fall. Warm summer temperatures slow their growth or even send them into dormancy, so seedlings are not likely to become established during periods of hot weather. Also, grass seed germination is directly affected by day length, and the seeds of most lawn species are not adapted to the long days of summer. Weed pressure is another challenge -- stressed out grass seedlings cannot compete with rapidly growing warm-season weeds.

Select the Best Species

• No common lawn grass is truly well adapted to summer seeding, but some species offer better chances of success. Tall fescue (Festuca arundinacea) is the most heat tolerant of the common cool-season grasses and it is also somewhat drought tolerant. Recommended for U.S. Department of Agriculture hardiness zones 3 through 8, tall fescue has a moderately short germination period which makes it easier to keep the soil moist while the seeds are germinating.

  Warm-season grasses in general are better adapted to summer conditions. Unfortunately, most of these grasses are difficult to establish from seed. Two warm-season species that are somewhat well suited to summer reseeding are Bermuda grass (Cynodon spp., hardy in USDA zones 3 through 11) and buffalo grass (Buchloe dactyloides, hardy in USDA zones 5 through 8).

Eliminate Weeds the Easy Way

• Weeds often grow more vigorously than turfgrass seedlings even when weather and soil conditions are optimal for grass growth. This problem becomes vastly worse in summer, when conditions favor many weeds and discourage lawn grasses. It is much easier to reduce weed pressure before you reseed your lawn. This means tilling up your lawn area and performing shallow cultivation every two weeks, as many times as possible before sowing your grass seed. These periodic cultivations destroy weeds that germinated during the previous two-week interval, so they gradually reduce the weed-seed population in the top few inches of soil.

Seeding Without Tilling

• You need to irrigate and fertilize to encourage robust, vigorous grass seedlings that are better able to compete with weeds and endure stressful summer conditions. This is especially important if you plan to reseed without the weed-control benefits of tilling up your existing lawn. For summer seeding, Michigan State University Extension recommends applying enough lawn starter fertilizer to supply 1 pound of elemental nitrogen per 1,000 square feet; this application will also add 1 to 1.5 pounds of phosphate. Irrigation should keep the soil consistently moist, but not soaking wet. Mulching with weed-free straw can help to protect soil moisture from bright summer sunshine and drying winds.