We all have dreams of thick, lush grass in our yards, but reality doesn’t always measure up. Maybe you’ve got some bare spots scattered around or perhaps you’re looking to beef up your current lawn to an overall fuller appearance. Or maybe you’re starting from scratch and you have a blank canvas. What you need is some new grass, ASAP!
So how long does it take for grass seed to grow? Expect to see new growth appearing between 5-30 days after planting. Many variables affect grass seed germination and growth, including the grass type, local climate, seed quality, seed freshness and care after planting. Cool-season grasses, like fescue and ryegrass, tend to grow more quickly, while warm-season types, like Zoysia and Bermuda, take more time.
In this article, we’ll break down that generalized timeframe in much greater detail, and we’ll also cover how to determine whether you need cool-season or warm-season grass. Plus, you’ll find the answers to when you should plant your new grass and tips on how to go about the planting process the right way.
Let’s dive in!
How Long Does It Take for Grass Seed to Grow?
The primary determining factor of how long it takes for grass seed to grow is whether it’s a cool-season or a warm-season type. It’s easy to assume that all grass seed is basically alike, but there’s more to the story.
“One of the biggest keys to success is picking a high-quality seed that is right for your climate. Not all grass seed is created equal,” says Trevor Lively, president of the landscape irrigation company Blue Jay Irrigation. “While looking for all different types of grass seed, you will be choosing between two types of grass: cool-season or warm season-grass.”
Trevor continues, “Cool-season grasses grow abundantly in places where there is a large difference of temperature during the year, where the warm season grass thrives in warm weather with less temperature difference.”
So depending on where you live, you’ll have better results from either a cool-season or a warm-season grass type. Here’s a visual that lays out the geographical areas more clearly:
If you live in the transition zone, that means your climate has elements of both the north and the south, and you’ve got more flexibility in the grass you can grow. For example, Zoysia grass is a warm-season type that germinates in 14-21 days. Tall fescue is a cool-season type that germinates in 7-14 days. Both of these grasses grow well in the transition zone.
Cool-Season Grass Growth Timeframe
Cool-season grasses take about 5-20 days to germinate, 30 days to get established and 2 months to be ready for mowing. Here are the most common cool-season grasses and their average germination timeframe:
|Kentucky Blue Grass||10-20 days|
|Perennial Ryegrass||5-10 days|
|Fine Fescue||7-15 days|
|Tall Fescue||7-15 days|
|Bent Grass||7-14 days|
|Creeping Red Fescue||7-21 days|
|Sun & Shade Mix||7-15 days|
Warm-Season Growth Timeframe
Warm-season grasses take 10-30 days to germinate, 2 to 2.5 months to be mow-able and almost a year for full establishment. Here are the most common warm-season grasses and their average germination timeframe:
NOTE: St. Augustine is a common grass for lawns in the Southern United States, but it is not available in seed form. This is because each plant produces a low seed yield, so there’s just not enough to be available commercially. So if you want St. Augustine grass, you’ll have to purchase grass plugs (like these from Sod Pod) or sod strips/blocks.
7 More Factors That Can Affect Grass Seed Growth Rate
Besides the grass type, 7 additional factors can affect grass seed growth rate:
- Age and Quality of Seed
- Hardiness zone
- Soil type
- Soil nutrients
Let’s look at how these factors affect grass growth rate and how you can fix any problems associated with them.
1. Age and Quality of Seed
Grass seed does have a shelf life. Older seed may germinate more slowly or have a decreased overall germination rate, so using it can really slow down your landscaping plans.
When you purchase your grass seed, be sure to look at the testing date on the bag. You’ll have somewhere between 10 and 18 months for the best germination rate for that seed. Beyond that, the growth rate will drop.
Also, higher-quality seeds tend to germinate faster and grow better than the cheaper varieties, so it’s worth investing in the best seed your budget allows.
2. USDA Hardiness Zone
Hardiness is an important factor to consider when choosing grass seed as the temperature ranges can affect growth rate.
Even within the larger categories of cool-season and warm-season grasses, some varieties are better suited to certain localized regions than others. This is especially true if you live in the more extreme northern or southern areas.
Use the USDA hardiness zone to find your zone and match it to the best grass seed for your area. Grass seed should have temperature charts listed on the bags. Pay close attention to these charts since they’ll be very helpful in determining which grass does best in your hardiness zone.
3. Soil Type
Soil type can be the difference between a uniformly thick lawn or one with patchy, sparse growth.
Soils with a fine, loose texture, like naturally sandy soils or those high in organic matter, are the easiest for tender grass roots to penetrate and establish themselves, fescue types in particular.
However, soil that’s too sandy may be lacking in some naturally-occurring nutrients, so you’ll need to replace those through fertilizing.
On the other hand, compacted soil or soil with a heavy clay component is difficult for tiny roots to break through. So your grass growth may be slowed or even stalled completely if you don’t amend dense soil into a more aerated state.
But the good news about clay soil is that it’s often very high in nutrient levels, so you may need less supplemental fertilizer. A few good grasses for clay soil include buffalo, annual ryegrass and Bermuda.
So it’s critical to learn what type of soil you have to work with, and prepare it accordingly before you put down any seed.
Watering can make or break your grass seed growth rate. Too little water slows down germination by keeping the seed hull dried out and tough, while too-wet soil can also inhibit the germination process. Also, giving too much water at one time can flood the area and wash your seed away.
To get the right water balance, use a light mist when watering seed for the first week or so, just enough to get the soil dampened. As new growth occurs, you can turn up the water a bit for a proper soaking without causing any puddles.
This video from Turf Mechanic offers some great tips on watering frequency both right after seeding and for newly-germinated grass:
Certain grass types are more tolerant of either shade or sun, so choose the one that’s best suited to your lawn’s light exposure to get the best and fastest results.
If you’ve got very little or no shade to your yard, pick a grass seed that does well in bright sunlight, like Bermuda or tall fescue.
For shady lawns, go with grass that thrives in shade, like Zoysia or ryegrass.
6. Mulch/Protective Covering
Mulch’s primary benefit for fresh grass seed is retaining moisture in the soil. But it’s also helpful for keeping the seeds in place and deterring birds from stealing your seed.
There are several good mulch options to choose from:
- Peat moss
- Screened compost
- Straw mulch
- Sawdust (in a very thin layer)
Some commercial formulas combine fertilizer and mulch, like this formula from Greenview. This can be a convenient option, but it does cost more than natural mulches like straw or peat moss.
7. Fertilizer / Nutrients
Grass seed also needs nutrition, in the form of fertilizer, for optimal growth.
When looking at a fertilizer bag, you’ll see various combinations of NPK ratio. These numbers signify the concentration of key nutrients: nitrogen (N), phosphorus (P) and potassium (K).
Here’s the breakdown of what each nutrient does:
- Nitrogen: Speeds up growth and makes grass green.
- Phosphorous: Contributes to root growth, which is key for your newly seeded lawn.
- Potassium: Help grass resist diseases and tolerate drought conditions. It can also promote winter hardiness for cool-weather grasses.
For new grass, you’ll need a specialized formula known as starter fertilizer.
Starter formulas have a high phosphorous component for healthy root development. You may see NPK ratios like 25-23-4 or 10-18-10. However, you don’t want too much of this nutrient since it is usually already present in soil, and excessive phosphorous levels can damage local ecosystems.
On the other hand, standard lawn fertilizers contain high percentages of nitrogen for vibrant green color, which is perfect for established lawns. They may have an NPK ratio of something like 16-4-8 or 33-0-2, which is not ideal for new grass growth. If new grass gets too much nitrogen, the seedlings will focus energy on producing blades instead of roots which will lead to weak root systems. Also, excessive nitrogen may promote weed growth.
The Best Time to Plant Cool and Warm Season Grass Seeds
The best time to plant grass seed depends on 2 main factors:
- Soil temperature
Let’s look at both in more detail.
Plant at the Right Soil Temperature
When temperatures get too high or too low, it affects root growth for both cool- and warm-weather grasses:
- Cool-season grasses need soil temperatures between 50 to 65 degrees Fahrenheit for optimal germination.
- Warm-season grasses prefer to germinate in soil temperatures between 70 and 85 degrees Fahrenheit.
And don’t try to press your luck with these guidelines. Cool-season grasses will not germinate/grow well when soil temperatures are too high. By the same token, warm-season grasses will not make progress when soil temperatures are too low.
The most accurate way to measure the soil’s temperature is with a thermometer. These devices have a temperature-sensitive probe and an analog display screen, and they provide easy and accurate results. Two good options include the Vee Gee Scientific 82160-6 and the AcuRite 00661.
Here’s how to use one:
- If your seeding site has very dense, compacted soil, use a sharpened stick or another pointed object to make a hole several inches deep. This helps protect the tip of the thermometer’s probe. If your soil is already loosened, you can skip this step.
- Insert the probe about 4-5 inches into the soil.
- Allow 5 minutes for the thermometer to reach a stable reading.
- Take one reading in the morning and another in the afternoon, then calculate the average of the two temperatures.
- If you’re seeding a large area, take averaged readings from several locations.
Plant in the Right Season
Now let’s look at the best time to plant grass seed for cool-season and warm-season grasses.
- Plant cool-season grass in the fall
- Plant warm-season grass in the spring
According to Penn State Extension, the cool-weather grasses slow down their root growth when soil temperatures are higher than the desired range of 50-65 degrees F. This is why they grow best in the cooler temperatures of the fall.
But like any plant, freezing temperatures will kill the grass blades, and cold weather can also damage immature roots. Plant your cool-season grass about 45-50 days before your first expected frost date to give the grass a chance to get established freezing temperatures hit. If you’re unsure of the first frost date for your area, you can find out from the National Weather Service.
Springtime is ideal for planting warm-season grasses whose shallow roots can’t survive cold winter days.
Make sure there will not be any danger of frost in your region before seeding your lawn. This map from the National Oceanic and Atmospheric Administration can help you determine the last estimated frost date for your region.
How to Plant Grass Seed for Fastest Growth
In this section, we’ll cover the two types of seeding you’re likely to do:
- Planting seed on bare ground
- Overseeding an established lawn
Planting Seed on Bare Ground
Whether you’re converting ground into a lawn for the first time or ripping out old grass for a from-scratch rebuild, there are a few key steps to getting your grass off to the best start possible:
Step 1. Do a soil test. Making sure your soil contains the right nutrients to support your new grass is an essential first step. You’ve got a few options to get this done:
- Go the DIY route with a soil test kit, like this probe tester from Kensizer.
- Contact your local cooperative extension to ask about their soil testing programs. This tool from the National Pesticide Information Center can help you find your county contact information.
- Order a collection kit from SoilKit. This is similar to getting a test done through the extension office, but it may be faster and less expensive (depending on your extension office’s pricing).
Step 2. Prepare the soil. For your seeds to have the best chance of success, the soil should be as smooth and fine as possible.
First, remove rocks and pull large weeds.
Next, turn the soil about 6 inches down. You could do this with a shovel or pitchfork, but an electric or gas tiller makes the job much easier.
If you’re using a tiller, make your first set of passes in one direction (east to west, for example) then making another set of passes perpendicular to the first (north to south).
Remove all roots left in the ground, and smooth the soil surface with a rake. Add any nutrients that may be lacking from the soil test. If your soil test was normal, apply a standard lawn-starter fertilizer formula.
Step 3. Choose the right amount of seed. Use the right amount of seed to cover the square footage needed for your new lawn. The amount you’ll need to cover your lawn’s square footage depends on the type of grass you choose and the quality of the seed itself.
Consult the directions on your seed package and follow the guidelines listed. This calculator can help you get a preliminary idea of how much see you’ll need for your lawn’s square footage:
Step 5. Water appropriately. Do this twice a day (or set your automatic sprinklers to 5-10 minutes twice to three times per day) for about the first week. Once seedlings emerge, reduce the watering frequency to twice weekly.
Step 6. Don’t mow too soon or too short. Wait until your new grass seedlings are at least 3 inches tall, and if you can hold off until they reach 4 inches, even better.
Lawnmowers generate a bit of negative pressure, or suction, as they pass over the grass. If you attempt to mow before your seedlings have the chance to develop a root system, they could get sucked right out of the ground. But once the seedlings have reached 3-4 inches in height, they’ve put out strong roots that keep them anchored in place against the pull of the spinning mower blades.
When mowing, don’t remove more than 1/3 of the grass height. This ensures that your grass still has plenty of green material left after being cut, so the plant can make food via photosynthesis.
Overseeding an Established Lawn
Another form of planting grass seed is a technique called overseeding. This is used for an existing lawn that has small bare patches, is a little thin or when you want to choke out the weeds and brighten your lawn.
Here’s how to do it:
Step 1. Do a soil test. Just like for a bare-ground planting, you need to know the status of your soil’s nutrition. Use one of the methods outlined above and replace the nutrients as needed.
Step 2. Mow your grass on the lowest deck height setting and bag the clippings. The taller the existing grass, the greater of a barrier it can be to your new seed making good contact with the soil.
Set your deck to the lowest setting available, and either bag the clippings with your lawnmower collection bag or do it manually.
Step 3. Rake or dethatch. This step removes excess organic matter from the soil surface, again with the goal of your new grass seed getting direct contact with the ground.
Thatch is dead grass, old bits of fallen leaves and other organic material that builds up on the soil surface. The thatch layer is actually beneficial since it adds nutrients and helps retain moisture, but it shouldn’t be more than 1/2 to 1 inch thick. You can determine how thick the thatch layer is by taking a slice of soil from your yard and measuring the brownish layer of matted roots.
If your thatch layer is more than 1 inch thick, you’ll need to remove some of it by raking or using a dethatcher.
Step 4. Rake bagged topsoil into the grass. Add a thin layer of fresh soil to your lawn to increase the soil-to-seed ratio, and therefore, the chances of germination.
But use a light hand here: You only need a very thin layer, about 1/4 inch at most. Rake it gently into the existing grass, making sure to spread the soil evenly with no clumps.
Step 5. Apply the seed. Use a hand spreader or a walk-behind one depending on the size of your seeding area.
Step 6. Fertilize, water and mow appropriately. Apply a starter fertilizer and water twice daily until you see new growth, then reduce the watering frequency to twice a week.
The existing grass provides a protective cover for the new grass, so you don’t have to wait quite so long to mow after overseeding as you do after planting on bare ground. You can safely mow once the new growth reaches 1 inch in height, which is typically about 2 to 3 weeks after planting.
Understanding Grass Seed Germination
Different types of grass vary in their natural germination rates, but all grass varieties require 4 key elements to grow:
- Light exposure
When these elements are balanced, the tough seed coat splits apart and baby root tips emerge in search of nutrients and moisture. Once the seedling puts down some primary roots, it sends up green blades that absorb sunlight for photosynthesis.
That’s grass seed germination in a nutshell, but you can check out this article on Nature’s Seed for a more detailed explanation.
Appropriate soil preparation and after-planting care meets each of these germination/growth needs. If even one element is out of balance, your new grass seed will take longer to sprout or not grow at all. So research and wise planning is essential!
Frequently Asked Questions about How Long It Takes Grass Seed to Grow
A lush, green lawn is a point of pride for most homeowners, and waiting can be the hardest part. But once you know what to expect in terms of how long it takes for grass seed to grow, you can adjust your expectations and make sure your new grass is on track each step of the way.
We want to hear from you! Do have any favorite tips to share about how to get grass seed established quickly? Have there been any strategies you’ve tried that haven’t worked very well? We learn as a community, and your question or experience may be exactly what someone else is looking for. So please share your thoughts in the comments!