You may be planning to fill in bare spots you see as the yard comes back to life in the spring, or you may be seeding a whole bare area that has no established grass. No matter the situation (fall for cool season grasses, spring for warm season grasses), having the grass thrive depends on some very important factors that cannot be ignored unless you want to waste your time and money. Let’s explore those factors.
Know Your Zone for Growing Grass
Want the best chance possible at a lush, green lawn that chokes out weeds on it’s own? Where you live greatly influences what type of grass will thrive and the best times to plant grass seed. The National Arboretum has a plant hardiness zone map that shows a large number of hardiness zones. This map can be greatly simplified for grasses because grass falls under two categories: cool and warm season grasses.
To get the most out of this guide, find your state on the map then continue reading.
Are You Applying the Right Grass Seed?
If you are in the cool zone, read the cool seasons grasses section, then scroll down to the grass seed timing section for cool grasses. If you are in the transition zone, read both the cool-season and warm-season grasses section, decide which grass type appeals to your situation, then scroll down to that grass timing section. If you are in the warm zone, read the warm season grasses section, then scroll down to the grass seed timing section for warm grasses.
Cool Season Grasses
If you live in the cool or transitional zone, cool-season grasses are the best choice. The most distributed and common cool-season grasses are Kentucky Bluegrass, tall fescue, perennial ryegrass, and fine fescue. These grass varieties grow best in the spring and fall when soil temperature averages 60-75 degrees F. You may be thinking, “that’s fine, but what type of cool-season grass should I get?” Any of these varieties thrive well in cool and transition zones, so take a look at the grass descriptions to evaluate what you would like to have most in your yard.
Kentucky Bluegrass has a high cold and heat tolerance, is shade and drought tolerant, and has good traffic tolerance. This type of grass does spread, so it has the ability to fill in bare spots over time. This grass is characterized by rich, dark green leaves. Due to it’s slower germination rate and higher water requirements, it takes a long time to establish and requires more maintenance throughout the year than other grasses in this group. Genetically modified seed is available (though more expensive) to reduce maintenance requirements of this grass.
Like Kentucky Bluegrass, tall fescue has a high cold and heat tolerance and is shade and drought tolerant. It differs from the other cool-season grasses by the fact that it has the highest traffic tolerance of the group. This grass type is popular in many grass mixes sold by home-improvement retailers. Tall Fescue only has a limited ability to spread and is considered a bunch-forming grass.
Fine fescue has low heat but good cold, drought, and foot traffic tolerance. This grass provides the best shade tolerance of the cool-season grasses. Fine fescues come in creeping and bunch-forming varieties, and sometimes, both can be found in seed mixes.
Perennial Ryegrass has a low cold, drought, heat, and shade tolerance, but has a high foot traffic tolerance. This grass is the fastest germinating of the group, which is why it is used so often in home-improvement stores’ cool season grass mixes. This is also a popular option for the warm zone so that in the winter when the warm-season grass goes dormant, the perennial rye becomes active.
Warm Season Grasses
If you live in the warm zone, warm-season grasses are the best choice. Transitional zones can have warm-season grasses thrive, but their grass will have a longer dormant period in the winter than warm zone. Generally, warm-season grasses will become dormant when the average soil temperature is below 60 degrees F. This can be appealing to some homeowners though, as a large lawn of perfectly groomed tan grass is attractive. The most distributed and common warm-season grasses are Bahia, Bermuda, Centipede, St. Augustine, and Zoysia.
Bahiagrass thrives along the Gulf coast states where the soil is loosely packed, sandy, and acidic. This grass loves humidity, making it difficult to maintain in the transition zone. It has a very spread-out (not dense) style of growing, which can be a magnet for weeds to fill in the gaps between grass clusters. Bermudagrass a spreading grass, and is characterized by pointy, wide leaves with a very light green color. It has the longest germination period of the group, at 21-28 days.
Bermudagrass has the shortest germination period of the group, at 4-12 days. It is characterized by pointy, narrow leaves with a dark green color. This grass type thrives in acidic, well-drained soil conditions. It has the fastest growth rate of any grass in this group, so keep the fact that you may be mowing twice or more a week if you have a lawn full of this grass. Bermudagrass is not a good choice for the transition zone due to its poor cold tolerance.
Centipedegrass has the slowest growth rate and can handle the highest acidity soil of the warm-season grasses. Its germination period is 14-20 days, and when well-established, provides a very low amount of maintenance to thrive. It does not, however, handle long drought periods well, nor can it handle overseeding with perennial rye (due to its shallow root structure). This grass is characterized by broad leaves and is light green in color. Keep in mind that keeping this grass green requires a large amount of iron, and should be applied through iron-rich granular fertilizer or iron-rich liquid plant food at intervals throughout the season.
St. Augustine Grass
This grass is unique in that it is the only grass out of the group that is sold exclusively to homeowners as sod. It is extremely difficult to grow this grass from seed, which is why seed manufacturers avoid selling it to the public. It is characterized by its dark green color and broad leaves. St. Augustine grass is another type of grass that loves moist, acidic soil, and can thrive in shade. A couple of big negatives to this grass type are that it has poor tolerance to foot traffic, and if exposed to very cold temperatures for long periods of time, it will die instead of going dormant.
Zoysia grass thrives in the transition and warm zone. It is the best grass out of the warm season grasses that can handle the conditions in the transition zone. This grass has a germination time of 14-20 days, which is right in the middle when compared to all the other popular warm-season grasses. It is characterized by light to medium green leaves and is a spreading grass. Zoysia has a deep root system which is very efficient at holding water, reducing its watering requirements greatly when compared to other warm-season grasses. It is important to point out that zoysia builds a thick thatch layer. This layer needs to be dethatched each spring to allow for the grass to recover during its peak growing period.
Timing for Cool-Season Grass Seed
Fall is the best time of the year to plant grass seed for cool-season grasses. The target average soil temperatures of 60-75 degrees F for germination for the first few weeks can be maintained without risk of extreme spikes in temperature. An added bonus is grass has time to become established and receive its pre-winter fertilization before it goes dormant for the winter.
If planting in the Spring, there is a higher potential for the grass to fail while it is still young due to temperature swings. If temperatures averaged 60 degrees for a few days then dropped 30 degrees overnight or spiked 30 degrees higher during the day, the new grass would have a very hard time surviving the extreme swings. There is also a much greater chance with the amount of average rainfall in April and May that the new grass will die from root rot before it can become established. Lastly, the lawn with new grass will require more water throughout the first season.
The timing for planting grass seed should always depend on the average soil temperature. While there has been success with grass seed growing in the spring, it is much easier for the homeowner to grow and sustain the new cool-season grass when it is planted in the fall.
Timing for Warm Season Grass Seed
Spring is the best time of year to plant warm-season grasses. The ideal soil temperature should be above 65 degrees F, and there should be no chance of any frost occurring. It is important to no fertilize warm-season grasses before stolons (horizontal stems) can be seen. For mowing, it is very important that frequent mowing at the recommended height for the grass (following the ⅓ rule) occurs for the first season. Doing so will maximize turf density, aiding in the hardiness of the new grass. Planting in the fall is not recommended for any warm-season grasses because average temperatures will be below the 80-95 degrees F that allow for optimum growing conditions.