When deciding when you will plant your grass seed, you may wonder “Can new grass seed survive a frost?” The best times of year to plant grass are often early spring and fall. There is still risk of frost during these seasons, especially in northern climates. I’ll share information about how frost impacts grass seed and provide tips for success when spreading grass seed with a risk of frost.
So, Can New Grass Seed Survive a Frost?
The short answer is yes. But while frost will often not kill or destroy your grass seed, it’s still best to avoid planting the seed when a frost could occur. This is because if your grass seed has germinated, the frost will likely kill your tender new grass seedlings.
The seeds themselves will likely survive and be able to germinate when warmer weather arrives. However, any seeds that have started to germinate won’t be able to survive the frost, rendering the seeds that they sprouted from useless.
So how can you avoid grass seedlings dying to frost?
Plant Your Grass Seed at the Right Time
The proper time to plant your grass seed depends on your climate and the type of grass seed you are using, but making sure it isn’t too cold for your grass is key.
Cool-season grasses should usually be planted between March and the middle of June, or between August and October. With cool-season grasses, it’s crucial that the soil isn’t excessively hot or cold. If it is, the seeds won’t germinate properly.
Most cool season grasses require soil temperatures of at least 55 degrees to germinate well. Your soil has likely reached this threshold if you have 7-10 consecutive days with air temperatures reaching 60 degrees Fahrenheit or above.
For fall planting or overseeding, ensure you plant your grass seed a minimum of 45 days before the first frost is expected for the year. This gives seedlings the time they need to grow strong enough root systems to survive frosts that arrive and endure through a long winter.
A good fall lawn fertilizer that’s high in potassium can help as well. Potassium helps plants handle extreme swings in temperatures and is especially valuable for grass in the fall.
The Best Time to Plant Cool-Season Grass
In general, most cool-season grass varieties grow best in the late parts of the summer and the early fall. Look for air temperatures that are between about 60- and 70-degrees Fahrenheit. You should plant the seeds during the day, preferably when the outside temperature is approximately 75 degrees.
What About Warm-Season Grasses?
With warm-season grass, you need to ensure that your soil temperatures will stay at a minimum of approximately 70 degrees Fahrenheit. You should plant warm-season grass seed in the later parts of the spring and in the early summer when daily air temperatures are a minimum of about 80 degrees Fahrenheit. Warm-season grasses can then establish their roots prior to any threat of frost.
Prepare Your Soil Properly
Properly preparing your soil is essential for healthy grass growth when planting grass seed.
No matter when you’re planting seeds, your soil likely won’t deliver a beautiful lawn if it hasn’t been properly prepared.
Test the soil’s pH and nutrient levels to make sure your seedlings will have what they need to thrive. It’s also recommended to make sure your soil has activated microbes and correct aeration.
Your soil’s pH can be between 6.2 and 7.0 for proper germination of your grass seeds. If the pH is lower, that means it’s too acidic. If it’s higher, that means it’s too alkaline.
You can adjust soil pH through product application. For instance, lime will lower soil acidity and can be applied with fertilizer, and sulfur will increase the acidity of your soil.
I like to do a soil test (I use this kit from Amazon) to get an overview of what my yard has in abundance, and what I should add to support my lawn grasses.
Remember to Water Consistently!
Don’t underestimate how important consistent watering is after you’ve just planted grass seeds. Germination is impossible if you don’t keep them consistently moist for a minimum of 2 to 3 weeks after planting.
Be especially mindful of this with warm-season grasses, as grass usually needs more water when temperatures are higher. Ensure that you water the area of lawn you have seeded a minimum of two times every day.
Take Care of Your Lawn All Year
It’s best to apply a pre-emergent weed product in the spring. For example, many homeowners use a crabgrass preventer. A lot of weedkillers will kill any crabgrass already in your lawn and prevent any new crabgrass from developing.
Continue treating for weeds throughout the spring and pull any you see as they start to grow.
It’s a good idea to check the pH of your soil again in the summer. This is vital for your lawn’s health.
When the winter arrives, there are products you can use to help protect your lawn.
Cold Stratification – Part of the Natural Growth Cycle
Can new grass seed survive a frost? Yes.
In nature most seed falls from plants in the fall, lies dormant over the winter and then germinates when soil warms in the spring.
That said, under certain circumstances, frost can cause significant harm for your grass seed.
Wide temperature fluctuations are harmful to new grass seed. Beyond the fact that grass seed won’t germinate unless temperatures are warm enough, there are other concerns with frost.
If there are several cycles of freezing and thawing, the water that comes from melting frost will gather and surround the seeds. When this happens, mold can grow and seeds can rot.
This side-effect from frost can do more harm to seeds than frost itself.
Seedlings are More at Risk in Frost than Seeds
Counterintuitively, planted seeds that have not yet sprouted as seedlings are probably safer than ones that have started to grow. That’s because seedlings are especially vulnerable to freezing and can be killed by cold temperatures.
Grass still in the seedling stage, have roots that aren’t yet deeply established enough to withstand the freezing temperatures. Even a single light frost can cause a lot of damage. The roots can quickly freeze, and when they’re frozen, they’re unable to absorb any water.
Understanding Your Yard’s Micro-climate
Your unique environmental conditions are the biggest variable in determining when to plant grass seed, and every yard is different. Houses right next to one another can have different conditions dictated by soil structure, shade, wind exposure, and more.
Most homeowners in northern lawns or within the transitional zone will want to plant new seed in late summer or early fall, when it is starting to cool but there is no risk of frost.
The threat of frost comes when you try to plant in spring before your typical last frost date. A week or two of unseasonably warm weather in March or April can cause some homeowners to jump the gun, and when that late spring frost comes, the money you spent on seed could be wasted.
While you can have success with spring lawn seeding projects, this risk to your seed investment is one reason why I recommend waiting until fall.