We’ve just entered the optimum seeding window for cool-season grasses throughout the state of Indiana. Though seed will germinate at a wide variety of temperatures, the optimum temperatures for germination are in the table below. The temperatures listed are air temperatures which would be almost identical to that in on the surface of the soil barring radiation effects. Realize though that optimum temperature for seed germination can vary depending on seed age, cultivar, etc. Also the optimum germination temperature of certain species may not involve a specific temperature but a rhythmic alternation of temperatures. Additionally, the maximum and minimum temperatures for seed germination are poorly defined because of the extreme slowness of germination, especially for the minimums. Most of our cool season grasses can germinate almost throughout the summer, so there are many other factors control the success of seeding. Poor irrigation, diseases like damping off, and weed pressure are the most common causes of seeding failures. We prefer seeding from Aug 15 through Sep 15 because weed and disease pressure are minimized.
| Optimum Temperatures for Seed Germination | |
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| Turfgrass Species | Optimum temperatures for seed germination* |
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| Creeping bentgrass | 59-86 |
| Annual bluegrass | 68-86 |
| Kentucky bluegrass | 59-86 |
| Rough bluegrass | 68-86 |
| Tall fescue | 68-86 |
| Red fescue | 59-77 |
| Sheep fescue | 59-77 |
| Chewings fescue | 69-77 |
| Perennial ryegrass | 68-86 |
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| *Temperatures separated by a dash indicate an alternation of temperatures. The first number is for approximately 16 hr and the second for approximately 8 hr, which would translate into cooler temperatures in the 16 hours of evening through morning followed by the 8 hours in the heat of the day. Adapted from Beards Turfgrass Science and Culture. | |