When you’re seeding your lawn for the season, you might be wondering, “will frost kill grass seed?”
While frost won’t kill grass seed that’s just been spread, it will kill seedlings that are beginning to sprout. This is because seeds have a strong shell protecting them in extreme weather; once they grow, the shell is broken.
However, there’s more to this topic than what you probably know. If you’d like to know more about protecting your grass seed during frost, keep reading!
Will Frost Kill Grass Seed That Was Just Spread?
If you’ve just spread your grass seed in late spring, only to find the forecast predicting frost, you might be worried it won’t make it.
However, you shouldn’t give it much thought. Grass seed only germinates in specific temperature ranges, and if it’s too cold, it won’t have the chance to grow from the start.
Depending on your hardiness zone and personal preference, you might start seeding in late spring, late fall, or late winter. Each choice comes with its advantages and drawbacks.
You can decide based on the hardiness zone you live in, the grass seed variety you’re choosing, and the amount of work you’re willing to put into the grass-growing project.
Deciding to spread your grass seed in the spring means that you’re at least 90% sure the last frost has come and gone. It also means your soil temperature is gradually rising.
Warm-season grass varieties only grow when soil temperatures are above 70℉. Any lower, the seeds will “hibernate” and only grow when the temperature reaches a favorable spot.
For those who live somewhere warmer, it’s best to try and seed your lawn a bit later since birds and small animals might eat the seeds before they germinate.
Some might prefer late summer or early fall seeding when the ground is still warm from the summer sun. You should check to see when the first frost is expected and plan the seeding at least six weeks before it.
It’s advisable to water your seedlings frequently when they’re growing. Once they’re strong enough, infrequent, deep watering helps to strengthen the root system and prevent the growth of weeds.
Late winter seeding, also known as dormant seeding, is the practice of putting your grass seed in the ground before winter is over.
This is good practice because it helps pull the seeds deeper into the ground, thus preventing shallow frost from affecting the growing seedlings in late spring.
Cool-season grass seeds will remain dormant until soil temperature reaches about 50℉. This usually translates to 60℉ in air temperature.
The optimal soil temperature for cool-season grass varieties is between 50 and 70℉. This is why the gradual change of seasons from winter to spring yields the best-looking lawns.
However, if you live somewhere with fluctuating temperatures, where there are frost and thaw cycles, this might not be for you.
Frost that accumulates around the seeds and then melts creates the perfect environment for mold growth. This means your seeds will rot in the ground before sprouting.
It’s also worth mentioning that grass seeds tend to withstand the cold well, but growing seedlings don’t. Their fragile root systems don’t reach deep into the ground to find water and nutrients.
This means that warmer days might encourage the seeds to grow, and then frost can come and freeze surface soil, actively killing the seedling.
That’s why we mention some steps you can take below to care for the growing grass seedlings, so they don’t have to suffer during the harsh weather.
How to Protect Grass Seedlings from Frost?
There are a few steps you can take that will prevent frost from affecting your grass seedlings and help minimize yield loss.
Taking Care of the Soil
This is an obvious step, but it’s worth mentioning. Soil quality ultimately decides the yield and lushness of your grass, so it’s essential to take care of it.
Check your soil pH and adjust it to fall between 6.2 and 7.0. This is crucial if you want both your roots and blades to be strong and withstand any weather conditions.
Aerating the soil is also highly recommended before and after you sow the seeds. This dramatically increases the surface area that receives water and nutrients and allows for better root growth.
You can do this by using a rake before and after spreading the seeds, or after the seeds have started germinating a spade to lift sections, then drop them in the same spot.
Adding fertilizer of the slow-releasing variety can help your grass grow longer and stronger. It also maintains the integrity of the soil and prevents depletion.
Organic matter like compost is great before tilling and sowing the seeds, especially with clay-rich soil. It helps break the ground up and prevent water retention that might lead to the seeds rotting.
It might sound counterintuitive to add water to an already frosty situation, but here’s the thing: water is an excellent insulator!
Watering your yard overnight will prevent frost from freezing the surface soil since liquid water must be at least 20 degrees warmer. It also has to give up latent heat to freeze.
The idea is to set your sprinkler system on once every hour/hour and a half for just 10–15 minutes.
This will provide the seeds with enough warmth to ward off frost while keeping the soil moist for optimal seed-growing conditions.
Covering the Lawn
This is also a great way to seal in the moisture and heat to prevent frost from killing your grass seedlings.
While some people use a thin layer of peat moss or straw as a seed covering, you can also use some plastic sheets or a cloth tarp.
The advantage of peat moss and straw is that they don’t suffocate the seedlings and provide the soil with some nutrients. However, they can also carry weed seeds and cause an unnecessary problem.
Plastic sheets and tarps can be heavy on some growing seedlings and need to be removed before the sun rises, so they don’t trap excess heat. But they provide excellent protection for the seeds and almost entirely ward off frost.
Avoiding Foot and Machinery Traffic
Frost accumulates inside the plant structure on a molecular level because it’s just solid water. If you step on a blade of grass that has shards of ice in it, it’ll most certainly break.
This is why it’s advisable to avoid walking or operating lawn mowers on the areas with seedling growth until frost subsides. You’ll macerate the leaves under your shoes if they’re still growing.
It might be difficult for little children to understand that concept, but bringing in a blade of grass and showing them how fragile it is might drive the point home.
Another critical step is to prevent competition between your grass and weeds.
It’s an unfair fight since weeds tend to have a larger temperature range than grass. So, the weeds in your yard might get a head start before your grass and leave it starving for water, space, and food.
Start by spreading a weed preventer, which prevents their seeds from germinating and laying roots. Then, it’s a matter of keeping an eye out for possible growths.
Weeds have relatively shallow root systems, so pulling them out won’t be too difficult. Just make sure you’re doing it often and thoroughly.
When Should Grass Be Cut for the First Time?
The virgin lawn mowing session should be once your grass blades have reached at least 3.5 inches in height.
In the first few cuts, avoid shortening it too much, as the blades are what make the food for the root system via photosynthesis. If the leaves are too short, the grass won’t take summer heat very well.
After you’re done mowing the lawn, remove the clippings. This is a very important step for your growing lawn.
If you leave them on the ground, they’ll dry out and turn to a thatch that will block sunlight from reaching your growing grass. They might also trap moisture and cause rot.
Since grass clippings don’t decompose on their own, add them to your composting pile so they’re useful in the future.
Sowing grass seed can be quite tricky if you don’t know whether it’s safe from frost and harsh weather or not.
However, if you were asking the question, “will frost kill grass seed?” right after you spread them for the season, you shouldn’t worry too much.
Seeds are complex systems that protect plant DNA and allow it to remain dormant until favorable conditions arise. If the weather is too cold, they won’t germinate.
The more fragile step in their growth is the seedling, which can struggle with frost quite a bit.
If you’re worried about the weather killing off your grass, follow the few steps mentioned in this article, and hopefully, your yield will be as lush and strong as ever.
Ben has a bachelor’s degree in construction engineering. When not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies, you can find him at home with wife and two daughters. Outside of family, He loves grilling and barbequing on his Big Green Egg and Blackstone Griddle, as well as working on projects around the house.
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