What Temperature Does Grass Seed Need To Germinate?

Grass needs to be planted at an optimum temperature to develop. If it isn’t exposed to the right temperature conditions, the seedlings may die, or the grass may give way to pests and weeds. 

If you’re wondering what temperature does grass seed needs to germinate, several factors come into play, but I’ve found the ideal temperature is between 50-60°F for cool-season grasses and roughly 65°F to 70°F for warm-season grasses.

The following guide will help you determine the optimal temperature and time to plant grass seeds for them to germinate.

So, just what temperature do grass seeds need to germinate? 

The answer depends on the type of grass that you’re using. The ideal temperature for grass seeds to germinate is between 60 to 75 degrees Fahrenheit. Keep reading, as we’ll cover the best seasons and temperature ranges for planting grass in this article.

Timing Is Important

To grow strong grass as quickly as possible, you’ll need to plant the seeds in optimal growing conditions. Grass grows best in different climates depending on the type of grass that you use.

Cool-season grasses grow best in cooler temperatures. These occur at the end of summer and the beginning of fall. Some of these grasses include Kentucky bluegrass, tall fescue, and perennial ryegrass. They do well in cool northern climates and in transition areas where warm and cool areas intersect.

Warm-season grasses grow better in warmer temperatures, such as at the end of spring and the start of summer. These can include Bermudagrass, Centipede grass, and Zoysia grass. Warm-season grasses grow best in both southern and western locations. They also do well in southern transition areas.

Best Temperature To Plant Cool-Season Grasses

Cool-season grasses are best planted in fall, as the start of fall brings soil that is still warm from summer. The soil is warm, while medium-day temperatures and cooler nights provide optimum conditions for growth. Here’s a list of cool-season grasses to check out.

The best soil temperature for cool-season grass is around 50-60°F. This approximately matches daytime air that is 60°F to 75°F. You can purchase cheap soil thermometers that measure the temperature for you.

The best time to plant grass occurs earlier the further north you travel, as fall temperatures become cooler earlier.

A good rule of thumb is to find out the rough date of the first fall frost. Plant your cool-season grass seed a minimum of 45 days before this date, before the temperatures become too cold. Doing this will ensure your grasses will grow throughout fall, and then grow once more in spring.

Cool-season grasses are next best planted in spring, as long as the soil and air warm up again. If you go down this route, do take care. Late snow and spring rain can make the soil too wet and cold, giving weeds the chance to sprout.

Your grass seeds also won’t have enough time to rest before the temperature starts to rise. Your seeds will stop germinating at these higher temperatures, so your cool-season grass will cease growing.

Best Temperature To Plant Warm Season Grass

Late spring and early summer bring rain and warm soil with it. This is a good time to plant warm-season grasses, as the soil is moist and warm enough for effective germination. These grass seeds do well in air that’s 80°F and warm soil that’s roughly 65°F to 70°F. The list of warm-season grass options includes bermudagrass and zoysiagrass.

Just like cool-season grasses, the best time to plant warm-season grasses differs with each area. A lot of people first plant their seeds at the beginning of spring, but there is still a risk of frost at this time. It’s best to make sure that the frosty season has passed completely. Warm-season grasses don’t do well in wet or cold soil, so it’s best to ensure that the soil has begun to warm up.

A general guideline is to find out the predicted fall frost dates in your area, and then plant your warm-season grass 90 days before this date. You can find out predicted frost dates from a county extension agent.

If the seeds are planted later, they’ll stop growing once the temperature cools down after summer. If timed right, your warm-season grass will grow well under the heat of summer. They’ll continue to develop for the whole season, then become dormant at the onset of winter.

Things To Look Out For When Planting Grass Seed

If your timing is right, your grass seeds should settle and sprout well in optimum conditions. Well-cared-for grass can look different depending on the type of grass you use, where you live, and the weather conditions of the growing year.

Different grass types have various germination rates. For instance, warm-season Zoysia grass may need three times more time to grow than Bermudagrass. Cool-season Kentucky bluegrass also needs two to three times more growing time than tall fescue.

After planting grass seeds in optimum conditions, grass begins to sprout anywhere from seven to 21 days afterward. The grass will need three to four weeks to grow long enough to cut grass. It’s important to wait for all of the seeds to germinate before mowing.

However, if you plant your grass in the fall, you might need to wait until spring for the grass to become long enough. Some grass types like Zoysia grass need more time to fully develop.

If grass seeds aren’t well encased in the soil, they won’t heat up enough to begin germination. When you plant your seeds, make sure that you place them ¼ inch deep within the soil. As long as they stay at an optimal temperature, you should see them sprouting after three weeks.

As the grass seedling grows bigger, the seeds need to take in more moisture. To help them along, regularly spray the top half of the soil with some water. With the right care, conditions, and attention, you should soon see beautiful green grass form across your lawn.