To achieve the best possible lawn come spring, it typically means you need to overseed the preceding fall to fill in bare spots and thicken sparse areas. When it comes to timing this project, the most important thing is to keep in mind is not sowing seed too late.
When determining when it’s too late to plant grass seed, you first need to figure out the right time to sow grass seeds.
Generally speaking, most people overseed or seed a new lawn in September because the blistering summer heat is in the rearview mirror, and the frozen ground of winter is still months away.
In many cases, though, a later autumn seeding may make more sense. And in some instances, seeding shouldn’t happen in the fall at all, but in the spring.
What You Should Know About The Timing of Sowing Grass Seeds
Experts have extensively tested the best time to sow grass seeds at the National Turfgrass Evaluation Program (NFEP), and they have discovered the following.
- The timing cannot be generalized because there are several kinds of grasses used for lawns, and these different types are better suited for different climates based on how they grow. In turn, different planting times are ideal based on the grass type.
- For the sake of convenience, they can be divided into two broad kinds: warm-season grasses and cold-season grasses. As you may have guessed, warm-season grasses grow the most during summer and cold-season grasses during the cooler spring and fall.
Because the two different types produce the majority of their biomass at different times during the growing season, it’s reasonable you should sow grass seed at different times.
- Warm-season grasses should be planted in the spring.
- Cool-season grasses should be planted in the fall.
The goal with putting down seed is to time it just before the natural period of its most active growth (depending on the type of grass seed you’re using). By doing this, new sprouts grow fast and have a great start on establishing before they go dormant in the late fall.
Always time planting in regards to the seed type, and not the climate you live in. For instance, if you are overseeding a warm-season lawn with cool-season grass, always do it in the fall.
What happens if you plant your grass seed too early?
Grass seed planted too early will struggle with germination and early growth.
- If you plant warm-season grasses too early in the spring, the air and soil temps will be too cool (and possibly) wet for germination. The seeds can either die off, or if they do germinate, young seedlings are at higher risk for damping-off.
- If you plant cool-season grasses too early in the late summer or early fall, the temperatures will be too high, and seedling growth will slow or halt. Seedlings may also suffer from too little water in hot conditions.
Also, keep in mind that when plants are stressed from environmental conditions, they are more susceptible to insect pests and disease problems.
What happens if you plant your grass seed too late?
If you plant your grass seed too late in the season, you’ll shorten its period of “good” growth. The root system will not have had the time to work its way down into the soil well. The grass blades will not have had time to adequately establish themselves and harden for the upcoming winter conditions.
When the air and soil temperatures begin to drop in the fall, these plants are less equipped to handle dormancy than seeds planted earlier. Because of this, you will likely see an increase in winterkill, with fewer plants surviving to spring.
Optimal Temperatures to Plant Grass Seed
Timing is dependent upon temperature since this influences germination the most.
- Warm-season grass seeds germinate best when soil temperatures are 65-70°F or daytime air temperatures are above 80°F.
- Cool-season grass seeds germinate best when soil temperatures are 50-60°F or daytime air temperatures are 60-75°F.
Best Time to Plant Grass Seed By Turf-Growing Region
The right time to plant is just before the preferred season of growth arrives. If you time it correctly, you will find that most seeds will germinate and grow into healthy grass within their growing season!
Naturally, it would be best if you treated any time after this ideal point as too late to plant your grass seeds.
However, being a little late is still permissible and may work out okay if your seeds get favorable weather. On the other hand, it is entirely too late when your seed is trying to grow in adverse weather conditions.
A general guideline is to plant cool-season grasses 45 days before the first fall frost is predicted and plant warm-season grasses 90 days before the first fall frost.
The turf-growing region you’re in relates directly to the type of grass you should be planting.
What are the turf-growing regions?
The US is divided into five different turf-growing regions based on annual temperature differences and humidity levels.
- The cool, humid Midwest, Northeast, and Pacific Northwest coast.
- The cool, arid area spanning across the Intermountain West and the majority of the Great Plains.
- The warm, humid area in the Southeast.
- The warm, arid area in the Southwest.
- The transition zone overlapping the cool and warm regions.
“Cool” zones grow cool-season grasses, “warm” zones grow warm-season grasses, and the transition zone grows a combination of both cool-season and warm-season grasses.
When to Plant Grass Seed in Each Growing Region
The best month to put grass seed down depends on the type of grass you are growing.
- Cool-season grasses are typically planted in Northern areas in mid-August to mid-September. In the transition zone, plant mid-September to early or mid-October.
- Warm-season grasses are typically planted in Southern areas in April or May and May to June in the transition zone.
Midwest & Northeast
Mid-August to Mid-September
September to Mid-October
Mid-August to Mid-September
April to May
October to November
April to May
Mid-September to Mid-October
May to June
Midwest: Northern Illinois, Northern Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Northern Ohio, South Dakota, Wisconsin
Northeast: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont
Pacific Northwest: Oregon, Washington, Far Northern California, Southeastern Alaska, Northern Idaho
Cool Arid: Colorado, Idaho, Montana, Nevada, Utah, Wyoming
Warm Humid: Alabama, Florida, Georgia, Mississippi, South Carolina, Southern Texas
Warm Arid: Southern Arizona, Southern New Mexico, Southern Texas
Transition Zone: Arkansas, Southeast Colorado, Delaware, Southern Illinois, Southern Indiana, Kentucky, Maryland, Southern Ohio, Oklahoma, North Carolina, Tennessee, Virginia, West Virginia
Q. Is it too cold to plant grass seed at 40°F?
Yes, it is too cold for grass seed to germinate at 40°F.
Q. Can you plant grass seed in 90°F weather?
Cool-season grasses will not germinate in 90°F weather; they prefer air temperatures between 60-75°F. Warm-season grasses may germinate at 90°F but typically don’t grow when air temperatures are above 90-95°F.
Q. Will grass grow in 45°F weather?
Warm-season grasses (typically grown in warmer, Southern climates) will not grow in 45°F weather. They don’t become active until soil temperatures hit the mid-50s. Some cool-season grasses start growing when air temperatures are 40-42°F, but most prefer slightly warmer temps.
Q. Can I plant grass seed in 50°F weather?
Yes, you can plant in 50°F weather, especially if you are sowing cool-season grasses. They germinate best when daytime air temperatures are 60-75°F. Warm-season grasses germinate best when daytime air temps are above 80°F.
Q. How late in the fall can you plant grass seed?
Warm-season grasses go dormant when temperatures drop below 55°F. Cool-season grasses go dormant when temperatures dip below 40-42°F. If your local temperatures are above these thresholds, you can plant, but results may be lackluster.
Q. Can you put down grass seed in the winter?
Yes, you can sow seed in the winter. Putting seed down in the winter months is known as dormant seeding. Once the weather warms up in the spring, seeds will begin germinating.
Q. When is it too late to plant grass seed in the spring?
Ideally, you shouldn’t plant cool-season grasses once the soil temperature is above 60°F. Their growth slows considerably and may halt once air temperatures get too hot. If you are planting warm-season grasses, it really isn’t possible to plant seeds too late in the spring.
Last Parting Thoughts
So, the often asked, “when is it too late to plant grass seed” isn’t something you can answer with a quick or standard reply. Theoretically, grass seed can be planted as long as the air and soil are warm enough—yet not so hot—the grass type isn’t triggered to go into dormancy.
That being said…you want to plant just as the grass goes into the season where it grows the best, giving it maximum time to establish before winter dormancy. Therefore, it’s too late to plant grasses when you miss this growth window.
- Cool-season grass varieties should be planted in the fall once soil temperatures drop to 50-60°F. Once soil temperatures drop into the 40s, it’s too late to plant cool-season grasses, as the seed doesn’t have enough time to germinate, and seedlings establish before going dormant for the winter.
- Warm-season grass varieties should be planted in the spring when soil temperatures reach 65-70°F. Once the air temperature gets above 90-95°F, it’s too late to plant warm-season grasses as the heat causes growth to slow or halt, and seedlings can’t establish well before temps drop in the late fall.
If you want to have the best possible lawn in the Spring then that usually means you have to put down some extra grass seed in the fall but knowing when it’s too late to sow grass seed in your climate is one of the most important things to consider when it comes to timing.
Generally speaking most people overseed or seed a new lawn in the month of September because the highest heat of summer is in the rear view mirror while the frozen ground of winter is still months away but in many cases a later autumn seeding may make sense. Let’s look at the variables that should go into your decision to put grass seed down later in the year.
Cool season grass seed will germinate in soil that is at least 45 to 50 degrees and it will grow vigorously in soil temps between 50 and 65 degrees. Outside air temperatures can be much lower than this without affecting the grass so long as there is no frost. Frost or freezing temperatures can kill new grass seedlings if their root structure isn’t well established.
For people who choose to sow grass seed late in the Fall you have to check soil temps to make sure they are above 45 degrees and you will need to prepare the soil well to ensure the quickest germination speed and consistency possible for the seed you lay down.
To keep sprouts alive as temperatures dip in late October and November you will want to fertilize your new grass with both starter fertilizer to establish root growth and potassium to quickly build up the new grass’ ability to overcome stresses like cold weather, frozen soil, and snow compaction.
If early frosts and freezing temperatures are in the forecast then covering your sprouts with garden fabric or greenhouse plastic may be necessary to keep the grass warm and growing as late into the year as possible.
There’s still a lot to say about this topic though so let’s start with a video I created specifically to address this topic before we go into further detail.
If you have decided to grow grass from seed this season then the following articles on this site will probably be helpful either now or in a week or two when you get to that part of the process:
However, you can learn more about the germination rates of grass when spread on top of the soil on our article entitled Will Grass Seed Germinate on Top of Soil?
Expert recommend not growing the grass seed in adverse weather conditions because it actually makes it harder for the grass seed to grow in a healthy way. The growth of the young seed at this stage is actually what is going to decide the overall look and strength of your turf, and you don’t want to get it damaged by planting your seeds too late, do you?
How much grass seed do you need per square foot?
Now, figuring out the answer to this question is not too easy- you have to actually take all the above mentioned things into account. For example, if you use the right grass for a warm climate, and plant it at the right moment in a sunny spot, you might actually have to use very little seed!
You know what goes well with artificial turfs? Trampolines! A lot of people are afraid of using sprinklers with trampolines, and if you’re one of them, click here to read our article on Do Sprinklers Ruin Trampolines?