Bald and thin areas in lawns can show up at any time! How late is too late to plant new grass seed? After all, quality grass seed can be expensive.
Don’t waste your money and time by planting grass seed at the wrong time of year!
Warm season grasses versus cool season grasses
How cold is too cold? Well, that depends on your type of grass. Grass can typically be divided into warm season or cool-season grasses.
Warm season grass loves hot weather and thrives in warm climates. Cool-season grasses typically do better in areas with warm summers and cold winters. Here are a few of the most popular varieties of each type of grass.
Warm season grasses
- Bahia grass
Cool season grasses
- Kentucky bluegrass
- Fescue grass
- Perennial ryegrass
How cold is too cold for grass seed?
Even the most cold-resistant cool weather grasses refuse to germinate once the soil gets below 50 degrees Fahrenheit. If the temperature outside is around 60 degrees, your soil is probably about 10 degrees cooler.
Grass seed that is planted in cold soil will not germinate and will probably rot before spring arrives. Avoid planting grass seed if there is a frost, or even the risk of a frost, in the forecast.
At what temperature does grass seed stop germinating?
It just depends on what kind of grass seed you are planting! A cold weather grass, like Kentucky bluegrass, will continue to grow in soil temperatures down to 50 degrees. However, keep in mind that the ideal germination temperature for Kentucky bluegrass is between 59 and 86 degrees.
Once you approach freezing temperatures, even a cool season grass will go dormant and stop the germination process.
A warm season grass, like Bermuda grass, will only germinate in really warm weather. The soil needs to be at least 80 degrees for Bermuda grass to grow. It is best to avoid reseeding warm weather grass when the weather turns cool.
The bottom line is: whether you have warm season grass or cool season grass, all grass seed requires warm soil to germinate. Check your forecast, and look for a 10-14 day window where the daytime temperatures are at least 10 degrees above the optimal germination temperature for your grass seed.
Take all the guesswork out of the project with a soil thermometer.
How long does it take grass seed to germinate in cool weather?
Under the perfect conditions, grass seed will normally germinate in 5-30 days. There are many factors that affect this timeline, including grass type, soil type, and, of course, temperature.
Cool weather grass seed will take off and grow in cooler weather! Check the soil temperature. If it is warmer than 50 degrees, your grass seed can go from newly planted to a mature lawn in as little as 30 days.
Ryegrass and fescue are quick to sprout and may germinate in as little as 5-7 days in soil temperatures between 55 and 65 degrees Fahrenheit.
However, if the ground is too chilly, or you are planting warm weather grass seeds, the cooler temperatures can stunt growth or even halt the germination process.
A warm weather grass, like Bermudagrass, will germinate in 7-14 days in soil that is between 75-85 degrees Fahrenheit. If the soil is cooler, it will significantly slow germination. If the temperature is consistently below 65 degrees, the Bermudagrass may not germinate at all.
Can new grass seed survive a frost?
Newly sprouted grass seedlings are especially fragile. A frost can deliver a killing blow to young grass. It is important that the grass have time to reach a length of 2-3 inches before the first frost arrives. Take care to check the forecast for frost before you plant!
Will frost kill newly planted grass seed?
Frost may not kill the seeds, but the seeds will not germinate in the cold ground. Remember, the rule of thumb for planting grass seed is to plant only in soil that is at least 50 degrees Fahrenheit. The seeds underground may end up rotting before they even get a chance to germinate.
What about dormant seeding?
Dormant seeding is usually done in the coldest months of the year. The seeds remain dormant during the cold weather, then sprout when the ground warms up in the spring. Dormant seeding is low-maintenance! The seeds are already in the ground, ready for spring rains and sunshine. Often the soil is loose and dry in the winter, which makes planting easy and increases seed to soil contact.
If your soil is cold and the forecast shows frost, keep those grass seeds stored away for the spring! Don’t waste your time or money planting grass seed when the ground is too cold for germination and growth.