does frost kill grass seed

Does Frost Kill Grass Seed?

Having a lush, green lawn makes your yard look so much better so when your grass starts looking as though it’s going a bit sparse, you might decide to sow some more grass seed. But one of the things that a lot of domestic gardeners want to know is will frost kill grass seed?

Frost might not kill your grass seed or even damage them. However, once the seeds germinate, the frost could kill the delicate seedlings so, for this reason, we would advise against planting your seeds when it is too cold.

If you have sown grass seeds that haven’t germinated over the winter then they will likely be fine by the time spring comes around. They will then go on to germinate as normal but it’s still best to wait.

Planting your grass seed at the right time of year will make all the difference in how well it does. When looking at the answer to the question, does cold weather kill grass seeds, choosing the right time is one of the first things you should think about.

As we have discovered, cold weather won’t kill the seeds themselves, but if there is a frost then it will affect the seedlings. So planting too close to winter could spoil your results.

However, the right time to plant grass seed will largely depend on two things; the type of grass seed you are using and the local climate. In any case, you’ll need to make sure that it isn’t too cold to plant the seeds before you start.

Warm Season Grass

Warm season grasses prefer higher soil temperatures so provided the soil is over 70 degrees fahrenheit, you shouldn’t have too much of a problem. It’s generally best to plant warm season grasses in the late spring or through into early summer. This is because the air temperatures are a little higher at around 80 degrees which means the soil temperature will be just right for these grasses.

What’s more, planting at this time of year means that the grass seeds will have plenty of time to establish their roots before there is any chance of frost setting in and killing the seedlings.

Cool Season Grass

cool season grass

If you are growing cool season grasses such as tall fescue or bluegrass then you’ll need to make sure that you plant them either in the early spring between March and June. If you don’t plant at this time, you won’t be able to plant in the summer and will have to wait for fall to come around. Generally, speaking, planting later in the year should be done between August and October.

The reason for this is that, in summertime, the soil will be far too hot for the grass seeds to thrive and this means that they won’t germinate. However, if you plant too close to winter then you’ll have the same issues because of cold temperatures.

Normally you will find that a cool season grass prefers a soil temperature that is at least 55 degrees fahrenheit. You’ll be able to judge this by the air temperature. Once you have consistent air temperatures of about 60 degrees for at least a week, this indicates that the soil temperature will be just right.

Preparing Your Soil

You can get the timing just right but if you haven’t correctly prepared your soil then you’ll find that your grass seeds won’t do as well. Spending a little extra time making sure that the soil conditions are spot on will give you grass seeds the very best chance.

Soil should have the correct pH, good aeration and the right microbes for it to be perfect for your grass seed.

When it comes to pH, you’ll need to make sure that it sits between 6.2 and 7.0. You can check this using a pH test which you can buy online or in garden stores; they’re very easy to come across. If the pH level is higher than 7.0, this means that the soil is not acidic enough. But if it tests significantly lower, then it’s too acidic.

There are products out there that are designed to rebalance the soil so it’s worth looking for these before sowing any grass seeds. However, you can also use natural materials such as sulfur or compost to make the soil more acidic or lime to make it less acidic.

It is also crucial to properly aerate the soil and again, there are products you can buy that will loosen it. Although, using a good quality tiller will also perform the same job. Make sure that once you have loosened the soil, you rake it over to remove any debris or left over grass before applying the new seeds.

Do You Need To Protect Grass Seed From Frost?

f you have grass seeds that have not yet germinated then there’s really no need to protect them from frost. You can store grass seeds in freezing temperatures and still use them the following spring so just because they’re on the lawn, that doesn’t mean that things are any different.

However, if the grass seeds have sprouted, frost will likely kill the seedlings. In this case, you will need to take steps to protect them over the course of winter. Making sure that you cover the seedlings and keep the lawn well watered are both great ways to do this.

How Cold Does It Need To Be To Kill Grass Seed?

Since grass seeds that have not yet sprouted can handle below-freezing temperatures, it goes without saying that things have to get incredibly cold before the seeds will be killed off.

If you’re talking about germinated grass seeds then these will normally suffer if the temperature drops below 32 degrees which is why protecting them, as discussed above, is so important. The reason that the seedlings suffer is that a layer of frost develops over the lawn during the night and starves the seedlings of the nutrients and oxygen that they need.

It doesn’t take much for the top layer of soil to completely freeze over. In many areas, during winter, nighttime temperatures easily drop below freezing and even if this is just for one night, it can mean the worst for your seedlings.

seeding in spring

Seeding In Spring

For those of you that are going to plant cool season grasses like fescue and various types of bluegrass and ryegrass, you will need to make sure that you sow the seeds in fall. But, as with everything else we have discussed in this guide, you’ll need to make sure you get the timing just right.

Aiming to plant cool season grasses around six weeks before the first frost is your best bet. However, do be mindful to check the soil temperatures which typically need to be below 70 degrees. If you seed any later than this, you will find that the seeds might germinate but the frost will come while they’re still too young and unestablished to survive.

On the other hand, it is possible to seed cool season grasses too early in fall which means that they will become victim to temperatures that are still too warm. These warmer temperatures may dry out the grass and ultimately kill it.

Final Thoughts

If you want to make sure that your grass seeds do as well as possible then it’s essential to plant them at the right time of year.

If you’ve ever wondered will frost kill grass seed, then the short answer is no. That said, while the seeds may survive a frost, any germinated seeds won’t so it’s essential to avoid planting too close to the first and last frosts.

When you plant will also depend on the type of grass seed you’re using. Cool season grasses should be sown in fall while warm season grasses, like zoysia, should be sown in spring.

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Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.

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