The Time for Grass Seeds to Germinate

Updated November 21, 2016

Grass seeds germinate when soil temperatures favour their germination. For instance, cool season grass varieties germinate in the early spring. Whereas, warm season grass types germinate in the late spring. The time it takes grass seed to germinate after they have been sowed in the soil depends on their type. Understanding more about grass seed germination helps you know when to plant your turf and how long to keep the soil moist to ensure healthy seedlings.

Cool-season Grass Types

Cool-season grass types, like fescues, ryegrasses, bentgrasses and bluegrasses, germinate when soil temperatures reach 4.44 to 7.22 degrees Celsius in the spring, according to Purdue University. Gardeners who wait for late summer to early fall to sow their grass seeds risk inadequate soil moisture for seed germination due to the hot summer temperatures. In addition, it is important for grass seed to establish before cold winter temperatures. Check your soil temperature right after the last frost date.

Warm-season Grass Types

Warm-season grass types, such as Bermuda and buffalo, need soil temperatures between 65 to 75 degrees Fahrenheit in order to germinate. Typically, soil temperatures are warm enough in the late spring or summer months depending on your climate. This grass type is particularly sensitive to cold temperatures. By measuring the soil temperatures, gardeners pinpoint the best time to plant warm-season grass varieties.

Measuring Soil Temperatures

Soil temperatures are measured with a soil thermometer in the morning and afternoon. To measure the soil temperature, make a pilot hole into the first 6 inches of soil with a screwdriver. Place the soil thermometer inside of the hole. Cover the soil thermometer from the sunlight to prevent skewed results, advises Julie Day, writing for the website of syndicated house and garden columnist Danny Lipford. Take an average of both temperatures to achieve an accurate result. Make sure to check the soil temperature for four days to ensure that it remains consistent.

Grass Seed Germination Times

After lawns have been sowed with grass seeds, gardeners must keep the soil moist throughout germination. Grass seeds fail to germinate in dry soil. All types of grass seed have different germination times. For example, Bermuda grass germinates in five to 10 days, buffalo in 14 to 30 days, annual ryegrass in five to 10 days, creeping bentgrass in 10 to 14 days, Kentucky bluegrass in 14 to 30 days, red fescue in seven to 14 days and tall fescue in seven to 12 days, according to the University of California.

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