How cold is too cold for grass seed? | Jonathan Green (2024)

If you’re wondering how cold is too cold for grass seed germination use our rule of thumb and check the weather reports. If the daytime temperature is below 60°F then soil temperature is below 50°F, making it too cold; if there is frost or still a danger of frost, then it’s too cold. If it’s too cold, the grass seeds will likely rot.

Here at Jonathan Green we have helped people sow and cultivate lush green lawns for over six generations. So, we know when customers call to ask if it’s too cold for planting grass seed – that thus far, nobody gave them the correct information on their planting window. Or, they have already planted out of season and need our help urgently! For tailored advice, call or visit us for a fast and friendly fix for your lawn queries.

When it’s too hot or too cold for grass seed

Grass seeds like warmth to germinate and because both hot and cold weather stunts growth it’s good to think about soil temperature as well as air temperature plus the upcoming weather when you’re about to reseed, fix bare patches or start a lawn from scratch.

Warm-season grass growers of the South and Southwest sow when nighttime air temperatures are just above 65°F in Spring and get great results as things start getting hotter. However, smart cool-season grass growers with the best lawns keep their seed by until Fall.

Cool season grass seed gives you a year-round vibrant green lawn so it pays to get it right first time, at reseeding time and when there are bare or problem patches. These seeds need a soil temperature of 50 and no more than 65°F, but take care; we put down this grass seed in Fall (specifically we plant in September, or with care, October) instead of Spring with good reason. When it’s put down in spring, it’s highly unlikely you’ll have the right soil temperature causing the seed to germinate way too slowly. If you get a lot of rain, it will get waterlogged and rot, if the weather gets too hot too quickly the heat could prevent germination.

Not to mention, you should not treat your lawn for weeds until you have mowed the new grass four times. A springtime seeding can be done, but it needs careful planning, and could cause a little more heartache than any lawn should.

Your planting window closes at 50°F

Around September though, grass seed has plenty of time to germinate in warm soil, which is key for cool-season grasses. Whenever it does start to sprout the air temperature is dropping. As this happens it gets too cold for other seeds, plants and weeds, which go dormant, allowing your grass seed just enough warmth and plenty water to germinate, and the space to grow fast.

Fast growth before it gets too cold for the grass seed is what you need. That way you have young tender grass that is well established and ready for winter. Once the grass is up and can be cut to the usual 2 or 3 inches then it is ready to be mowed. This gives the grass a strong crown, and a good indication that your lawn will flourish in the summer.

So, when working with cool-season grass, planting in a soil temperature of below 50°F is too cold for grass seed. Like we said before, some folks need a different planting window so drop us a line before you prep your soil and we’ll help you get it rooted right first time.

How cold is too cold for grass seed? | Jonathan Green (2024)


How cold is too cold for grass seed? | Jonathan Green? ›

If you're wondering how cold is too cold for grass seed germination use our rule of thumb and check the weather reports. If the daytime temperature is below 60°F then soil temperature is below 50°F, making it too cold; if there is frost or still a danger of frost, then it's too cold.

How cold is too cold for grass seed? ›

Grass seed needs a warm temperature to germinate and grow. The ideal temperature range for grass seed is between 55-85°F (12-29°C). Anything below 55°F (13°C) will inhibit the growth of your grass seeds, so it's important to keep an eye on the weather forecast when planting.

What is too cold for seeds to germinate? ›

This means that the temperature is not dipping below 70 degrees Fahrenheit at night. If you live where the temperatures are getting down into the 30s, 40s, 50s, or even 60s at night, the soil is too cold to germinate these types of vegetable seeds.

Will frost stop grass seed from germinating? ›

Planting grass seed after a frost can be risky because the freezing temperatures can damage the seed and hinder germination. However, the exact impact of frost on grass seed depends on various factors such as the type of grass seed, the severity of the frost, and the current weather conditions.

Will seeds germinate at 50 degrees? ›

F – 60 deg. F if the moisture and oxygen levels are optimum. For example, parsley seeds could be planted and will germinate when the soil is 40 degrees but a greater majority of seeds will germinate at the 'optimum' temperature range for parsley seed germination of 50 deg.

Is 40 degrees at night too cold for grass seed? ›

``We recommend not planting grass seed until you have a consistent temp above 60 degrees during the day and do not have lows below 40 degrees,'' added Ketterling.

Should I water grass seed if it's cold? ›

The colder weather does not evaporate moisture from the lawn as quickly as it does in the warmer weather. Most lawn experts recommend watering your grass until the soil or ground temperature reaches the 40-degree Fahrenheit mark.

What temperature kills germination? ›

Within that range, it takes approximately 6 to 8 days before seeds germinate. Tomato seeds may still germinate at 50°F, but it will take over 40 days, and there will probably be no germination if the soil temperature is 104°F.

Is 60 degrees too cold to germinate seeds? ›

Most seeds prefer to germinate in a range between 60 and 90 degrees. Some seeds are so sensitive to soil temps that they won't germinate if the soil is too hot or cold. Spring crops tend to prefer cooler soils, and some crops will germinate even when the soil temp is just barely above freezing.

Does freezing affect seed germination? ›

We found that freezing temperatures and durations affected the germination. The rapid freezing with water at -20°C in the program freezer for 24 h followed by rapid thawing gave a low rate of impermeable seeds with a high rate of the normal seedlings.

What happens if you plant grass seed and then it freezes? ›

If an unexpected frost comes, that does not mean the seeds are ruined. Grass seed that has not sprouted will simply lay dormant in the soil until the temperature is right. The problem is when the grass seed has begun to sprout. Grass seedlings are not strong enough to survive a frost.

How many days does it take for grass seed to germinate? ›

Most grass seed will start growing in about 10-14 days, but sometimes it can take up to 30 days. When you're planting new grass seed in your yard, it can seem like it's taking forever to start sprouting.

At what temperature will grass stop growing? ›

Grass generally stops growing once temperatures drop to below the range of 50-55 degrees Fahrenheit or reach above 90 degrees Fahrenheit. Since soil takes longer than air to lose and retain heat, it will take a period of a least a few days for a temperature change to impact the growth of grass.

What temperature kills seeds? ›

Properly managed, a com- post pile should easily reach 140°F, which breaks down all organic matter, including weed seeds. Figure 1.

Can seeds survive 40 degree weather? ›

Freezing temperatures can kill some types of vegetable seeds. Ideal seed storage temperatures are between 40 to 50 degrees F. The percent germination declines at different rates depending on conditions and species.

Can seedlings survive 40 degree weather? ›

Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.

Will grass seed survive 40 degree weather? ›

If the daytime temperature is below 60°F then soil temperature is below 50°F, making it too cold; if there is frost or still a danger of frost, then it's too cold. If it's too cold, the grass seeds will likely rot.

Can grass seed grow in 40 degree weather? ›

Sometimes it is a bit of a waiting game at this time of year. The trick is to find the time when soils are unfrozen so that seed can be worked in slightly, yet air temperatures must be cold enough so the seed won't germinate. Wait for high daytime temperatures of 35-40 degrees before seeding.

Will fescue grow in 50 degree weather? ›

Fescue has its preferred temperature range for germination. It germinates best when the soil temperatures are between 50 and 65 degrees.

Does fescue germinate in 50 degree weather? ›

The optimal temperature for tall fescue to germinate is between 59-72 degrees F.

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