Frost will not kill grass seed that has not yet sprouted. Grass seeds are hardy and can withstand deep freezes without harm. However, grass seed that has just sprouted into a seedling is easily killed by frost. Young grass seedlings are delicate plants with shallow roots. A single frost can starve and destroy new grass roots. For this reason, it’s important to only seed your lawn when there is no upcoming risk of frost.
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Do You Need to Protect Grass Seed From Frost?
There is no need to protect unsprouted grass seed from frost. Grass seeds that are stored in subzero temperatures (such as in your garage during winter) will not be harmed. Similarly, grass seed on your lawn that has yet to sprout will not be damaged by frost, so there is no need to protect it.
- Grass seed that has not sprouted does not need protection from frost.
- It is safe to store grass seed in subzero temperatures.
- New grass seedlings are susceptible to frost and should be protected from cold weather.
While a grass seed that has yet to germinate is not at risk from cold weather, new grass seedlings can be killed by frost. If your new grass seed has already started to sprout and freezing temperatures are in the forecast, take these steps to protect your new grass from frost. A little bit of protection can save your entire lawn of new grass.
What Happens if You Plant Grass Seed Too Early?
If you spread grass seed on your lawn too early in spring, grass seed may sprout during a warm spell, only to be attacked by a late frost. This puts all the seedlings that have already sprouted at risk of being killed by frost. A single freezing night can kill all of your new grass seedlings. This is especially true of warm-season grasses, such as Bermuda, St. Augustine, and Zoysia.
- Grass seed that is spread too early in spring may sprout during a warm spell, then be killed by frost.
- A few species of cool-season grasses can be seeded early by using these tips.
- Warm season grass seedlings are easily killed by frost.
However, there are a few grass types that are resistant to damage from this freeze-and-thaw cycle. Winter-hardy cool-season grasses can be seeded in winter. They will sprout once temperatures warm up in spring and a fair number of the seedlings will survive a late frost. This process of dormant seeding only works if you are seeding the right grass type, such as Kentucky Bluegrass, Ryegrass, and Fescue. It’s important to note that even these varieties will perform better when they are seeded during warmer temperatures.
When Should You Seed Your Lawn to Protect From Frost?
It’s essential to seed your lawn when there is no risk of frost on the horizon and soil temperatures are ideal for grass seed germination. Because you can overseed your lawn in either spring or fall, it’s important to know the right timing for both these seasons.
Spring Grass Seeding Timing
Warm-season grasses perform best when seeded in spring. However, it’s essential to wait until the danger of frost is past. Warm-season grasses are the most likely to be harmed by frost. Plan to seed once average soil temperatures rise to 70℉ (21℃). This is typically the point in spring when daytime highs hit 80℉ (27℃) for the first time that year.
- Seed warm season grasses in spring.
- Warm season grasses include St. Augustine, Bermuda, Zoysia, and Centipede grass.
- Wait until soil temperatures rise to 70℉ (21℃) to seed your lawn in spring.
Grass seed that is seeded too early in fall can be killed by a late frost. Alternatively, cold soil in spring can prevent grass seed from sprouting for a while. This makes it easy feed for flocks of birds that begin migrating in spring.
Fall Grass Seeding Timing
Cool season grasses, such as Kentucky Bluegrass, Tall Fescue, Fine Fescue, and Perennial Ryegrass actually grow best when they are seeded in fall, not spring. However, proper timing is critical. Make sure to seed at least 6 weeks before the first average fall frost. Additionally, wait until average soil temperatures have dipped below 70℉ (21℃) to seed. This typically lines up with daytime highs around 75℉ (24℃)
- Seed cool season grasses in fall.
- Spread grass seed at least 6 weeks before the first fall frost.
- Average soil temperatures of 60–70℉ (16–21℃) are ideal for cool season grass seeding.
- Seeding too late will expose cool season grasses to killing frosts.
Seeding cool-season grasses too early in fall exposes your seedlings to hot, dry conditions that can easily dry out and kill your new grass. On the other hand, seeding your lawn too late means your seedlings will be exposed to killing frosts before they’re well-established. Although some tough grasses can survive a light frost, you’ll still lose a lot of new grass by seeding too late in the year.
How Cold Does it Need to Be to Kill Grass Seed?
A grass seed that has not yet germinated is so hardy that many species of grass can survive temperatures that dip below 0℉ (-18℃). So, it takes extreme cold to kill a grass seed. They’re biologically designed to survive the winter and sprout in spring.
- Grass seed that has yet to germinate can survive extreme cold below 0℉ (-18℃).
- Newly sprouted grass is at danger of being killed whenever temperatures go below 32℉ (0℃).
- A nighttime frost freezes the top layer of soil, where seedling roots are. This starves the seedlings overnight.
Young grass seedlings, on the other hand, are quite fragile. Temperatures below 32℉ (0℃) are cold enough to freeze the top layer of soil. When this happens, your baby grass can’t pull any moisture or nutrients from the ground. A single cold night is enough to starve grass seedlings long enough to kill them.