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weed and seed end of summer

Typical seasons to grow new grass are in the early fall and spring when temperatures remain mild, but it is possible to establish a lawn during the heat of summer. Planting grass by seed or sod in June or July requires some extra care to ensure that the seedlings have enough moisture for healthy growth. It is critical to choose active, summer-growing grasses for your yard to have a successful lawn installation.

With hot summer temperatures come pesky weed seeds. As you establish your grass, especially if seeding, you need to hand-pull any emerging weeds. These plants steal nutrients and moisture away from your struggling seedlings. One way to help smother weed seed germination and conserve soil moisture at the same time is using peat moss. By applying a thin peat moss mulch layer across your grass seeds, they retain their moisture while stopping weed seed germination due to lack of sunlight.

Warm-Season Grasses

Warm-season grasses, such as Bermuda grass (Cynodon dactylon) and St. Augustine (Stenotaphrum secundatum), prefer warmer regions in U.S. Department of Agriculture plant hardiness zones 7 through 10 and 8 through 10, respectively. You have a greater chance of a healthy lawn establishment with these grass species because they actively grow during the summer while returning to dormancy in the cooler winter months. Choosing a cool-season grass species for establishment in June or July results in a dead lawn — these grasses are dormant in the summer and do not have actively growing roots for nutrient and moisture absorption.

Although you may have chosen a particular warm-season grass to plant, their establishment from seed is not rapid. In fact, full establishment may take between two and six months to achieve. However, proper soil care helps the germination process. For example, break up any clods and remove weeds from the planting site. With seeds spread into the soil to a maximum depth of 1/4 inch, you should use a lawn roller across the seeded area. This roller presses the seeds closer to the soil particles for better moisture contact. With the hot summer sun, the seeds need to be kept constantly moist until seedlings emerge.

An alternative to the seeding process is using sod. Most warm-season grasses are available in sod form so that you have healthy seedlings applied to your fresh soil. Similar to the seeding process, a lawn roller worked across your sod helps the roots establish in the ground. Especially with summer heat, you want the sod’s roots to have instant access to soil nutrients and moisture to overcome the stress of installation and hot temperatures. As a result, your lawn’s establishment is much faster compared to a seeding strategy.

Summer conditions make it difficult to establish new grass in lawns. Here are some tips if you can’t wait for fall.

If you have the time to take a soil test, follow the soil test recommendations for establishment. Homeowners can purchase a soil testing kit from the Michigan State University Extension bookstore. More information on soil testing can be found at MSU Soil

Weed control

Periods of high temperature, high relative humidity and heavy rains or overwatering can also make new seedings subject to devastating diseases such as Pythium blight. Finally, weed competition from summer annuals such as crabgrass, goosegrass and broadleaf bandits such as purslane, knotweed, clover and prostrate spurge can quickly take over a new establishment in the summer if herbicides are not used.

Summer is certainly not the ideal time to establish cool-season turfgrasses due to high temperatures, long day-length, disease pressure and especially weed competition. The optimum growing temperatures for cool-season turfgrasses are in the range from 60 to 75 degrees Fahrenheit, so occasionally during some of our warmer stretches of weather the nighttime temperatures might not even fall within this range. Long day-length or more hours of sunlight results in more hours in the day for drying the soil. Maintaining that delicate balance of soil moisture between too wet and too dry is more challenging during the summer due to the extended drying period.

If you’re still interested in establishing in the summer, keep on reading. If not, wait for the optimum establishment time of late August and early September.