Young grass seedlings are very vulnerable to cold weather. Because grass seedlings have not developed deep roots, a hard frost that freezes the upper layer of soil will prevent seedlings from getting water and nutrients, killing your new grass. If you have a yard with new grass and there’s an upcoming frost in the forecast, follow these tips to keep your grass alive and thriving:
1. Water Your Lawn
Although it may seem counterintuitive, watering your lawn before a cold snap will actually help the soil resist freezing. Water present in the soil will retain heat and make it less likely for the ground to freeze solid. For best results, water your lawn in the evening to protect your new grass overnight.
Go the extra mile. If you have the ability to set a timer for your watering system, program it to water for half an hour once every three hours overnight. The water coming from your tap is typically at least 20 degrees above freezing. By adding warm water at night, you will help prevent frost from forming. This is one of the best ways to protect young grass from frost.
2. Cover Seedlings
Because frozen ground can kill new grass, another great way to protect your grass sprouts is to help your ground retain heat during cold nights. In the evening, cover your new grass. Use tarps or cloth weighted down with a stone or spare lumber. Even a thin layer of black plastic tarp will help keep warm air close to the ground and prevent frost from harming your new grass. Remove the tarps in the morning to expose the grass to air and sunlight.
3. Avoid Walking on Your Lawn
There are few things worse for frosted grass than foot or vehicle traffic. Walking or driving across young, frosted grass can kill the grass. This is because the pressure on frosted grass causes frozen water molecules to tear through plant cell walls, severely damaging the grass blades. To protect new grass, prevent people and animals from walking on your lawn until the frost has thawed.
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Can New Grass Seed Survive a Frost?
Grass seeds can live through frost and freezes. Seeds have the ability to remain dormant in cold weather. They will lie inert in your lawn until temperatures rise again, at which time the seeds will sprout. If you have just seeded your lawn and see an unexpected cold snap in the forecast, don’t worry. Those seeds will simply wait for warmer temperatures.
While seeds handle frost very well, young grass seedlings are very vulnerable to freezing temperatures. Take care to seed your lawn at least 6 weeks before any expected frost. This will allow grass seedlings a chance to develop the deep roots they need to survive cold weather.
Does Grass Seed Freeze?
Grass seed will freeze if temperatures get cold enough, but this typically won’t damage the seeds. Frozen seeds will simply remain dormant, waiting for warmer temperatures before they sprout.
Think of the husk of the grass seed as armor—it protects the seed itself from extreme heat, cold, and even drought. Grass is at its most vulnerable when it has just begun to sprout and leave its armor husk.
Will Grass Seed Die if it Gets Too Cold?
If you’ve recently spread grass seed and it isn’t sprouting due to cold weather, this isn’t a cause for alarm. The seeds aren’t dead. They are simply lying dormant until temperatures rise high enough for growth. Grass seeds can survive an entire winter of freezing temperatures and sprout in the spring. Even if you seeded the day before a frost, your grass seed will survive.
One of the few ways cold weather can harm grass seed is if temperatures shift from freezing to thaw several times in a short period. This can cause rot which destroys grass seeds but is relatively rare in most regions.
Can You Plant Grass Seed Before a Freeze?
If you want to reseed your lawn in the fall, plan to do it at least 6 weeks before the average first frost. This is because young grass seedlings are easily killed by freezing temperatures. If you wait too long and your seedlings are just coming up when the first frost arrives, much of your new grass will die unless you follow the tactics listed at the top of this article.
What if it Freezes Right After You Plant Grass Seed?
If a frost or freeze occurs right after seeding your lawn, your seed will not sprout until temperatures rise. Any seeds that have already sprouted may die, but unsprouted seeds will remain dormant.
If temperatures do not rise in the few days following the frost, grass seed may lie dormant throughout the winter. This may not be ideal, because grass seeds left over the winter until spring are more likely to be eaten by birds and rodents over the winter months, resulting in a thinner spring crop of grass. For this reason, it’s best to seed your lawn in the fall at least 6 weeks before the first frost or wait to seed in spring once soil temperatures are above 60℉.
Does Grass Seed Still Grow After the First Frost?
Grass seeds operate by a simple biological mechanism: if temperatures remain steady above a certain point for a few days, they will sprout. This can occur at any time of year, including a warm period following the first frost.
- Cool-season grasses sprout when temperatures are between 50 and 70℉.
- Warm-season grasses sprout when temperatures are above 70℉.
- If temperatures rise to the “sprouting point” and remain there for 2–3 days, grass seeds will grow. This can occur following a first frost.
- Because first frosts are generally accompanied by alternating cool and warm periods as the weather shifts from one season to another, it’s not uncommon for grass seeds to still sprout after a first frost, or for a late-spring cold snap to attack young grass seedlings.
- Grass seedlings that have sprouted after a fall frost are at extreme risk for subsequent frosts—cold snaps kill young grass. That’s why it’s important to seed at least 6 weeks before the average first fall frost. This ensures your grass isn’t caught in this deadly cycle.
Will Frost Kill Grass Seeds?
Grass seeds are very resilient and can handle extreme cold without harm. After months of frost, freezes, and even snow, grass seeds will sprout once temperatures warm again.
On the other hand, immature grass seedlings are extremely vulnerable to frost. A single cold snap can often kill all the grass seedlings in your yard unless you protect them by watering, covering them to retain daytime heat, and/or making sure there is no traffic on your frosty yard. To get the most out of your seeding, plan to seed at least 6 weeks before the first average frost in fall and do not seed in spring until temperatures have remained steady above 60℉ for several days.