How Long Does Grass Seed Take to Grow?

Robert Pavlis

Most grass seed starts growing in about 10-14 days but it can take as long as 30 days. Here are some tips and tricks to speed up the growth of grass seed, as well as advice on starting a new lawn.

small grass seedlings
Lawn grass seedling growing fast, source: CSIRO

Factors That Affect Grass Seed Germination

Several factors affect the speed of germination for grass seed. 

  • Type of grass seed
  • Weather
  • Soil conditions

If you are trying to improve how long it takes for grass seed to grow, do what you can to control these factors. Start with the right kind of seed, sow when weather conditions match the type of seed you have and keep them from drying out. 

To keep the ground moist, water thoroughly a couple of days before planting so that the water reaches a depth of at least 6 inches (15 cm). Then water twice a day after sowing.

Type of Grass Seed

Each type of grass has a different germination rate in any set of conditions and cool-season grasses grow faster than warm-season grasses. This is mostly due to the fact that warm-season grasses germinate slower and take longer to develop a root system.

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Cool-Season Grasses

Type of grass Germination time Growth rate (inch/week) Seeding rate (lbs/1000sqft)
Bent grass 10-14 days 1-2 1
Fescue 7-14 days 2 6
Kentucky bluegrass 14-30 days 1-2 3
Rye grass 5-10 days 1-2 8

 

Warm-Season Grasses

Type of grass Germination time Growth rate (inch/week) Seeding rate (lbs/1000sqft)
Bermuda grass 10-30 days 0.5-1.5 1
Buffalo grass 14-30 days 1 3
Centipede grass 14-21 days 1 1
Zoysia grass 14-21 days 0.5-1 plugs*

* best planted as plugs, but can be seeded

Weather

Weather affects how long it takes for grass to grow because it impacts the temperature and moisture in the soil. Temperatures that are too high or two low will slow down germination and seedling growth. Both of these are also affected by too little or too much water in the soil.

Cool-growing grasses germinate best when soil temperature are between 50°F and 60°F (10-16°C), which matches a daytime air temperatures between 60°F and 75°F (16-24°C).

Warm-growing grasses germinate best when soil temperatures are between 65°F and 70°F (18-21°C), which happens when daytime air temperatures reach 80°F (27°C). As you might expect, warm-season grasses like it warner. Cold weather can interrupt the germination process and possibly kill young grass plants.

Soil Conditions

Soil pH doesn’t affect germination but it does affect the growth rate of the seedling after it germinates. Cool-season grasses prefer a soil pH in the 6.0 to 7.2 range. The warm-season grasses Bermuda and zoysia like the same pH, but centipede grass prefers a range of 4.5 to 6.

Lawns grow best in good quality of soil that is not compacted and contains a good level of organic matter. 

Cool-Season vs Warm-Season Grasses

Most grasses can be categorized as either warm or cool growing. The cool growers grow when it is cool, spring and fall, and go dormant in hot weather. Warm-season grasses are dormant in cool weather and grow best when it is warm. 

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Cool-season grasses are also better able to tolerate frost and low light. Warm-season grasses require less water and are therefore more suited for summer draughts.

graph showing cool-season grass growing spring and fall, warm-season grass growing in summer
Cool-season grass grows fastest in spring and fall, while warm-season grass grows fastest in summer, source: U. of California

Selecting the Right Kind of Grass

Select between cool and warm grasses based on your local temperature. Base your purchase on quality, not price. Seed that contains named cultivars is usually of higher quality. Certification is also important and indicates that seed has been tested, inspected and graded by accredited experts to ensure excellent germination as well as pest and drought tolerance. 

For a cool-season grass, select a mixture of types. This provides some that will germinate faster to help get the lawn going and it will also provide varieties that are better suited for both sun and shade.

map of the usa showing cool grass in the north and warm in the south
Regions in the USA suited for cool and warm grasses, source: Milorganite

Best Grass Seed for Shady Areas

Lawn grass likes lots of sun and is not really suited for shade. If you do have a shady area use a grass mix that is labeled for shade. This will normally contain shade tolerant cultivars which are more important than the type of grass. 

A good mix for cooler climates is tall fescue in combination with shade-tolerant cultivars of Kentucky bluegrass (80/20 ratio). The addition of fine fescue (hard fescue, creeping red fescue, and chewings fescue) is beneficial in low maintenance areas.

St. Augustine is a good warm-season choice for shade and zoysia is a close second. Bermuda is the least shade tolerant.

Keep tree leaves off the grass in winter especially in shady areas. Don’t believe the myth that leaves left on the lawn won’t harm it.

What is Coated Grass Seed?

Coated grass seed is a new product that offers some benefits at a higher price. It is seed that has been coated with a protective clay layer which keeps the seed moist and prevents it from drying out as fast. This should improve the germination rate especially in cases where watering is less frequent but the coating does not speed up germination. Some brands add a fertilizer, fungicide, or insecticide to the clay coating to protect and feed the newly emerged seedlings.

Because the coating adds weight and increases the size of the seed, you have to apply more volume and weight of seed, than with traditional seed. Keep this in mind when you are comparing prices. A bag of coated seed contains about ½ the amount of seed found in a bag of uncoated seed.

Endophyte-Enhanced Grass Seed

Endophytes are special fungi that form a symbiotic relationship with plants, grasses in this case. Unlike mycorrhizal fungi, endophytes can colonize the upper parts of plants including leaves and developing seeds. Seed containing endophytes can be produced and when it is planted, the fungi grows in the seedling, helping it grow. Such grass seed is now available commercially for some types of grasses.

Are these worth buying? They do work and they can help seedlings grow faster but they don’t affect the speed of germination. They also improve resistance to pests and improve stress tolerance.

The problem with these products is that storage becomes critical. When stored at 41°F (5°C) the seed lasts 2 years. On the other hand, “endophytic seed stored at 70°F (21°C) will lose 40% of its endophytes in 7 months and all of its endophytes in 11 months”. If you are sure the seed is fresh it might be worth buying but you may be better off with regular seed.

Dog Urine Resistant Grass

Ryegrass and fescue are the most urine resistant types of grass because they can tolerate higher nitrogen levels. Kentucky Bluegrass and Bermuda are the most sensitive and show dog spots more.

Do Dog Rocks Work? Read all about it in this post, Dog Rocks – Do They Prevent Lawn Burn?

Does Grass Seed Go Bad? 

Seeds are alive and just like every other organism they age and eventually die. Dead seed won’t germinate. For this reason it is best to use fresh seed and try to use it in the same season. A good quality seed will be useful for a couple of years but the percent germination drops every year.

Germination Test

It is easy to do a germination test at home. Place some seeds in a paper towel, wet it, place it in a plastic baggy and wait for germination. Fresh seed normally has a germination rate of about 85%. Older seeds can be much lower. Details for this test can be found in Germination Test: How to Test Seeds for Viability

Storing Grass Seed

Excess seed can be stored for use the following year but keep it cool and dry. Seed that is too moist is likely to develop fungal decay

Tips for Growing Grass Seed Quickly

How you plant a lawn affects how long it takes grass seed to grow. Do the following for the fastest growth.

  • Select the right type of seed for your climate.
  • Use fresh seed.
  • Pre-wet the soil down to 6” (15 cm) the day before seeding.
  • Plant at the best time of year for the type of grass.
  • Use the right amount of seed – don’t skimp on the amount.

When is the best time to plant my grass seed?

The best time to plant cool-season grasses is in early fall and the second best time is early spring. Some warm-season species can’t be grown from seed, but for those that can it’s best done in spring once temperatures warm up. 

Planting the Seed

Start by loosening the soil with a tiller or a rake. If you are going to use a tiller, consider adding a couple of inches of compost and digging it in. Don’t layer compost on top and try to seed in that. It has to be mixed in with the soil.

Apply the seed and rake it in. It is important that the seed is covered with soil, but avoid burying the seed too deeply. Seed that is just spread on top of soil will most likely dry out and die. 

Seed can be spread by hand, but a spreader gives you a more even distribution. If you use a spreader make several passes over the same area, in different directions.

Consider applying a thin layer of straw over the seed bed. This will shade it, keeping the seed cooler and reduce evaporation. This is not required but it does make watering easier. The straw can be removed after the seedlings are established and used as mulch in garden beds.

How Often to Water?

Water at least twice a day using a light, gentle stream of water. In warm weather you may need to water 4 times a day. Don’t water on a schedule – water when it is needed. You want the seed and soil moistened but not to the point where you form puddles. Puddles will cause the seed to float around and give you an uneven spread of seedlings. Keep watering until seedlings are several inches high. You do not need to water on rainy days.

When is the best time to water? Many say never to water at midday but that is a myth. Water when needed to keep the soil moist. 

Once the seed has germinated you can start watering less but reduce the amount and frequency gradually. This will encourage deeper root growth.

When to Mow a New Lawn?

Keep kids and pets off the lawn while the seed is germinating and until it is several inches high. Don’t mow too soon. The grass needs the leaf blades to make food so it can form strong roots. Wait at least a month after germination starts before you mow – longer is even better. Cool-season grass should be at least 4” (10 cm) tall before you mow.

FAQ

Q1. Is seed better than sod?

Both will create a great lawn. Sod is quicker and takes less initial maintenance, but is more work to install. It is also more expensive. Seed is slower, cheaper and needs careful attention in the first month or two. 

Q2. Will grass seed grow if I just throw it down?

Not very well. It will dry out very fast which slows down germination and if drying happens after germination, the seedling will probably die.

Q2. How do I keep moss out of my lawn?

Don’t try to kill the moss. Moss grows where other things don’t grow and it can grow in sun or shade. It also does not indicate that you have the wrong pH – that is another common myth.

The best way to get rid of moss is to grow better grass. Fertilize and water more so the grass grows and the moss will die out. In shady areas, overseed with shade tolerant grass seed.

 

Growing Great Lawns

Here are some other articles about your lawn.

Biological Liquid Dethatcher for Lawns – Do They Work?

How to Get Rid of Moss in Lawns

Lawns Reduce CO2 Levels

How To Add The Right Clover To Your Lawn

Does Liquid Lawn Aeration Work – Liquid Soil Conditioners?

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

6 thoughts on “How Long Does Grass Seed Take to Grow?”

  1. I always consult the weekly weather forecast when sowing grass for a meadow flower mix.
    I only sow when a few rainydays are forecast. I am just too lazy to water twice a day.

    Reply

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