Will Frost Before Germinating Hurt Ryegrass Seed?

Climate and Ryegrass

• Ryegrass and other cool season grasses are typically green in autumn through spring and lose their color in summer, growing best in temperatures ranging from 65 to 75 degrees Fahrenheit. Both annual and perennial ryegrass will grow in U.S. Department of Agriculture plant hardiness zones 3 thorough 9. Perennial ryegrass is sometimes sown over warm season grasses, a practice called overseeding, to give them color during the winter. Frozen ryegrass seeds will thaw and still germinate.

Best Seeding Temperature

• The best time to sow cool season grass seed is when daytime air temperatures are between 60 and 75 F and the soil temperate ranges from 50 to 65 F. The best time to sow ryegrass is in the fall when the temperatures are 75 F and falling or in the spring when temperatures are 60 F and rising. When temperatures are above 60 F at night and 90 F during the day, cool season grasses go dormant and lose their color.

Frost Seeding

• Farmers planting ryegrass for animal forage sometimes reduce seeding costs by “frost seeding.” Ryegrass seeds are conventionally sown 1/4 to 3/8 inch deep with a seed drill. To frost seed, farmers broadcast or scatter seed on frozen soil shortly after the spring snow melts. Frost seeding works best when temperatures drop below freezing at night and rise above freezing during the day. The seeds work slowly into cracks in the soil made by the freezing and thawing. In studying the practice, researchers at the University of Wisconsin found that most ryegrass seeds germinated, with the grass becoming well established. You can also use the frost seeding technique for overseeding turf grass.

Overseeding in Cold Weather

• If you live in a mild climate, take care not to overseed ryegrass too deeply in the winter at the risk of having it grow thin and spotty. Ryegrass seeds will germinate better if you plant them at least 1/4 inch deep. If you overseed turf in the spring, either conventionally or by frost seeding, do it early so the grass will have time to get established before hot summer weather arrives and the grass goes dormant.