Early September is crazy busy, with children going back to school, and the last long weekend in warm weather, or you’re harvesting your vegetable garden. It’s easy to forget to overseed your lawn during this optimal time. So you might wonder, could I just plant grass seed in the winter anyway?
You can plant grass seed in the winter using dormant seeding, if you wait until soil temperatures are consistently below 55F (12C). But if there’s a long enough warm spell, the seeds will germinate and die come the next frost. It may be better to wait until spring.
Can You Plant Grass Seed in the Winter?
Yes, you can sow grass seed in the winter, so long as the area isn’t covered in snow or ice, so the seed can make contact with the soil. Grass seed will survive low temperatures. In fact, freezing seeds is how seed banks protect their seed stores. Sowing seeds in the winter is a practice called dormant seeding.
The best time to dormant seed is right before snowfall and while the soil is somewhat workable. Snow cover will protect the seed and the cold temperatures will keep it dormant. When temperatures warm in the spring, the snow thaws and keeps the seeds moist.
The seeds will germinate once the ground warms up to a consistent 55F (12C). This can save you a lot of time come spring, or it can spell disaster, as you’ll find out below.
How Cold is too Cold to Plant Grass Seed?
It’s too cold to plant grass seed (unless dormant seeding) when the soil temperature is below 55F (12C), as it’s too cold to germinate. This means daytime temperatures of around 60F (15C), although a soil thermometer will give you the most precise measurement.
The other important consideration is how close is it to the first frost if seeding in the fall or the last frost if seeding in the spring. If planting in warm temperatures in the fall, does your grass have enough time to establish itself before the frost hits? It takes between 7 and 30 days for the grass to germinate, depending on species, and then another 60 days to establish itself.
If the first frost day is quickly approaching, then either wait until temperatures stay below freezing for dormant seeding or wait until spring. If you wait until spring, you’ll have better germination rates.
Can New Grass Seed Survive a Frost?
Dormant grass seed can survive a frost, but germinated seedlings can not. If you have a mid-winter melt where temperatures go above freezing for a time, grass seeds will sprout. (Where I live, we’ve had 4 springs before the last frost date!) But when temperatures drop again, the frost will kill them. You will need to clear the dead seedlings before seeding again.
If you plan on dormant seeding, later is better than earlier. That way you can avoid unseasonable heat waves ruining your work.
What’s the Best Winter Grass Seed?
For dormant seeding, the best grass seed is any kind of cool-season grasses. Pick the best mix of species or variety for your area. Warm-season grasses can’t take the lower temperatures, and wouldn’t germinate until well into spring, anyway. If you’re in a warm-season zone overseeding with cool-season grass, the best grass seed is annual ryegrass.
How to Improve Germination Rates of Dormant Seeding
Dormant seeding is rarely going to have as high of germination rates as seeding in spring or early fall. There’s too much that can go wrong (temporary thaws, birds, rotting). But if you want to increase your chances:
- Wait until soil temperatures are consistently below 55F (12C) before dormant seeding. If the seeds have enough warm days, they will germinate and die as soon as the frost comes. Between December and March is a good timeframe.
- If overseeding, rake the grass before you seed, removing debris and loosening the soil, to increase the chances of the seeds making direct contact with the bare soil.
- If seeding a new lawn, gently work the soil so it’s loose.
- Go have hot cocoa and let nature do its work. Like germinating grass seed in warm weather, stay off the lawn and don’t apply any herbicides, pesticides or fertilizers, whether organic or synthetic. If you seeded before snow cover, the snow will gently press the seeds into the soil.
- Remember that you have dormant seed on your lawn, so that when temperatures warm up, you can monitor the germinating grass and keep them moist for better germination rates.
Dormant seeding in the winter can come with substantial rewards (like getting a head start on your lawn), but it also comes with a lot of risks — low germination rates, false springs, and even birds eating the seed. It may be best to just wait until spring.