There are two types of grass seed: cool season and warm season. Each has an appropriate planting time. Cool-season grasses, which are typically grown in the Northern states, should be planted in the early spring in April or early fall, late August to early September. Broadcast warm-season grasses, which are grown in Southern states, in late spring, May, or early summer, June.
Use the soil temperatures as a planting guide. Warm-season grass seed can germinate in soil that is between 65 and 70 degrees, whereas cool-season grass grows best in a temperature of 50 to 65 degrees.
Broadcast seed in the North at least 90 days before the first frost is expected. In the South, 60 days before the expected frost is okay.