The Ideal Time To Reseed Your Lawn, According To An Expert

Whether you are renovating a weedy lawn or overseeding existing turf, timing is critical to establishing a healthy, robust lawn. Proper timing ensures good seed germination and allows grass seedlings time to establish a healthy root system before the environmental stresses of summer or winter arrive. In turn, a healthy grass stand is better able to compete against weeds and requires less maintenance. We visited with a lawn expert to learn more about the ideal time to reseed lawns, factors to consider, and techniques for achieving a lush and healthy lawn.  

Factors To Consider When Reseeding Your Lawn

Depending on where you live, your lawn may contain cool-season grass species, warm-season grass species, or a mixture of both. The active growth period for these two classes of turfgrass differs significantly and impacts the optimal time for seeding your lawn. “The goal is to establish deep root systems to survive the hot and dry summer season for cool season grasses and the hard, dry freezing weather for warm season grass,” said Craig McManus, host of The Garden Question Podcast and founder of McPlants, a boutique garden design-build company. “You do that by correctly timing the sowing of your seed.”  

Determine Grass Type

To get that timing down, you need to first determine which type of grass you wish to sow. Grass selection is largely dictated by local climate. Cool-season grasses such as fescue, Kentucky bluegrass, and perennial ryegrass are most active during the winter and early spring months. They flower and set seed by early summer and often go dormant during the heat of summer in southern states.  

Warm-season grasses are dormant in winter and have a flush of growth when spring arrives. They flower and set seeds during summer and into early fall, before cold weather returns. Warm-season grasses include zoysia, St. Augustine, centipedegrass, Bermudagrass, and buffalograss, as well as native grass bends. They thrive in heat and are the dominant turf type in southern landscapes, while cool-season grasses flourish in northern states. There is a broad transition zone across the center of the country where homeowners can grow both types of grass. In these areas, cool-season grasses are commonly grown in shady locations, and warm-season grasses in hot, sunny sites. 

Grass type is the primary factor influencing when to seed grasses, but local climate also plays a role. Spring and fall arrive at different times depending on where you live and may likewise be rainy or dry. It is best to use specific parameters described below to pinpoint the best time to seed the lawn in your area.

Best Time To Seed Your Lawn

Once you’ve determined which type of turfgrass(es) grow in your landscape, you can identify the best time to seed your lawn.

Warm-Season Grasses

If your lawn is composed of warm-season grasses like bermudagrass, zoysia, or centipedegrass, late spring to early summer is the ideal time to reseed. “With warm season grass it is best to sow seeds when nighttime temperatures reach 70 degrees consistently,” McManus said. This correlates with warmer soils to enhance germination and the absence of frost, which can kill seedlings. Spring and early summer plantings also allow grasses plenty of time to establish and promote winter hardiness before cold weather returns.  

Cool-Season Grasses

Early autumn is the ideal time to seed cool-season turfgrasses. “You will see the best results when seeding turf type fescue and Kentucky bluegrass at the beginning of the cool season, approximately ten weeks before the average [first] frost date,” McManus said. “This will give the young seedlings time to establish deep root systems over the growing season to fight through those hot dry months of July, August, and September months.”  

Spring is the second-best time of the year to seed cool-season turfgrass, however spring seeding offers less time for grasses to mature before the heat of summer sets in. If spring is the only window you have for establishing the lawn, you might consider laying sod instead of seeding, especially in southern states, as mature sod is more stress tolerant than a stand of immature seedlings. Note that timing may vary slightly when starting your lawn from sod or plugs. 

Overseeding Vs. Reseeding

The steps involved with seeding differ depending on your needs and goals. Lawns with just a few bare patches or a thinning stand can be overseeded to fill in the gaps. Landscape professionals also regularly overseed cool-season lawns as part of maintenance programs to keep weeds out and promote a lush, beautiful lawn. “With cool season grass, if you see 30% or greater soil then it’s probably time to overseed,” McManus said. Warm season grasses do not typically require overseeding. 

When lawns have become overgrown with weeds or show extensive bare patches, they may require a complete overhaul. “If you see 50% soil, I would start over in establishing the total lawn,” McManus recommends. This is where reseeding comes in. With reseeding, existing vegetation is removed to expose the bare soil, which is then prepared and heavily seeded to establish a new, dense stand of grass. The same process is used to establish a new lawn over bare (or weedy) soil.

Sometimes, grass is not the best solution for a difficult area. “I often find folks are expecting optimum results from less than optimum growing conditions,” McManus said. “The real solution may be to stop trying to grow grass in an area that will never support it.” Alternatives such as groundcovers, slope-stabilizing shrubs, and other plant materials may be a better option where grass continues to fail. 

Preparation For Seeding

When seeding your lawn, begin with a high-quality seed mix. Read the package label to determine the contents of the bag. In addition to grass seeds, many mixes also contain filler ingredients that can include weed seeds or “other crops.” The best strategy is to look for seed that has no weedy species or “other crops” listed among the contents. When purchasing seed for a cool-season lawn, consider using a mix of turf type tall fescues and improved Kentucky bluegrasses for a more resilient lawn.

As with any type of planting, successful lawn seeding begins with proper site preparation. The steps involved vary depending on whether you are overseeding or reseeding. When overseeding an existing lawn, start by mowing the existing turf to a height of two inches. Collect grass trimmings when mowing. “Before seeding, blow, rake, or vacuum out debris to maximize the seed to soil contact,” McManus suggests.

Soil preparation for reseeding and sowing a new lawn takes a little more effort. Start by killing and removing existing vegetation. Conduct a soil test to determine if you will need to amend the soil to adjust pH or nutrient levels.

“You’re wasting money if your seed doesn’t contact a prepared soil bed,” McManus said. “The deeper you can cultivate your soil the better your chance of establishing a healthy lawn.” Prepare the soil through core aeration or tilling 4 to 6 inches deep. “This allows moisture and oxygen into the soil and easier entrance for young roots.” Work any necessary soil amendments into the loosened soil and rake the seedbed smooth to ensure good seed to soil contact. 

It is also important to prepare bare spots for reseeding. “Bare spots may not be fixable by throwing seed on them. There could be rock or construction debris below the soil surface preventing deep root system development,” McManus said. Prepare these patches in the same way you would for reseeding, which will allow you to identify any problems hidden below ground. 

Seeding Techniques

The same equipment is used for overseeding and reseeding, but seed is applied at different rates. For both applications, use a drop spreader or broadcast spreader to distribute seed across the entire planting area. For even coverage, apply half the seed making passes with the spreader in one direction, then apply the second half of the seed in the opposite direction. It can be helpful to mix the seed with sand, Milorganite, or a similar material to help distribute the seed more evenly. 

With overseeding, the bulk of the lawn is still covered with grass and seed is broadcast over the top of the existing lawn. Apply seed at the label-recommended rate for overseeding. Application rates will be higher for reseeding the lawn. Use reseeding rates for treating bare patches. 

When seeding bare areas or reseeding, cover the seed with a very thin layer of soil, approximately 1/8 inch thick, by gently raking the area after spreading seeds. It can also be helpful to firm the soil around the seed using a weighted lawn roller, which can be rented at most equipment centers. This ensures good seed to soil contact. 

Aftercare And Maintenance

“Consistent moisture during seed germination and establishing a young seedling is critical,” McManus said. After seeding, keep the planting bed moist with light daily waterings for the first two weeks. Provide enough water to keep the surface moist, but not saturated. As seedlings emerge, reduce the frequency of watering and practice deeper irrigation. Prevent the area from fully drying out over the first few months as the small seedlings establish their root systems. It is also a good idea to keep falling leaves off cool-season grasses to avoid damaging the foliage. A leaf blower allows you to move the leaves without disturbing the seedlings.  

Young seedlings require nutrients to support development. Depending on your soil test results, you may wish to use a started fertilizer that is high in phosphorous. “Fertilize three weeks after seedlings have germinated,” McManus says. Make a second application around the ten-week mark, then resume regular fertilizer practices. Avoid mowing seed areas until the grass has reached a height of three inches, at which time regular mowing practices can be resumed.

With proper timing and care, you can establish a healthy, vigorous lawn in a single season. Understanding when to plant grass seed based on turf type and your location will ensure you get the best coverage. And remember to establish good seed to soil contact for optimal results.