When To Plant Grass Seed In Spring For A Lush Lawn

As the first signs of spring arrive, homeowners are eager to get the garden and lawn in shape. For turf areas, this often includes overseeding and reseeding existing lawns or starting novel lawns from seed. Proper timing is vital to establishing a lush, well lawn. Seeds and seedlings are at the mercy of their surroundings and require specific environmental conditions for optimal germination and growth. Excessive heat or icy can put undue stress on seedlings, but under the right conditions, grass seedlings grow quickly. Soil and air temperatures can support you identify the best time to plant grass seeds in spring. The exact timing will vary based on your location and the type of grass you are establishing.  

Types Of Grass And Their Planting Seasons

Lawn species belong to two main groups based on their vigorous growth phases: cool-season grasses and warm-season grasses. In Southern landscapes, warm-season grasses dominate. These include bermudagrass, zoysia, St. Augustine, centipedegrass, and buffalograss—species that thrive under sultry conditions and put on a flush of growth in spring and early summer. Cool season grasses are also grown in the South, primarily in shaded areas under huge tree canopies.

Cool-season grasses prefer cooler temperatures. In the South, they grow actively from delayed fall through early spring, providing vivid color all winter long. Cool-season grasses are the primary type grown in Northern lawns and include fescues, Kentucky bluegrass, and ryegrasses. In the North, vigorous growth occurs mainly in the shoulder seasons. They put on a flush of growth in delayed spring to early summer and again from delayed summer through early fall.

The best time to seed each type of grass is at the start of their vigorous growth phase. For warm-season grasses, this occurs in delayed spring to early summer, when air and soil temperatures are sultry and seasonal rains plentiful. Because cool-season grasses grow actively during cooler weather, their sowing time differs. The ideal time to seed cool-season grasses is in fall as air temperatures begin to frigid but the soil remains sultry.

Spring is the second-best time to seed cool-season lawn grasses, after soil and air temperatures begin to rise. Spring sowing can be challenging in the South. Growth tends to shut down during the balmy summer months, so you have only a compact window of vigorous growth in spring before summer temperatures arrive and stress juvenile seedlings. Weeds also grow quite actively during the spring, creating a great deal of competition. Summer entertaining and recreation can further stress juvenile lawns, but can be avoided by limiting foot traffic on establishing lawns.

Optimal Timing for Planting Grass Seed In Spring

Grass seeds require adequate moisture, favorable temperatures, and oxygen to germinate. Air and soil temperatures play an vital role in germination and growth of warm-season and cool-season grasses. The ideal conditions for lawn establishment arrive at different times, depending on your location. Take the guess work out of when to plant by keeping track of air temperatures and purchasing an inexpensive soil thermometer to measure soil temperatures.

Warm soil is key for germination of warm-season grasses. As a rule of thumb, wait until delayed spring to sow warm-season grass seed, after the threat of frost has passed and soil temperatures are consistently above 65°F. This generally corresponds to daytime air temperatures around 80°F but can vary based on slope and aspect. For example, north-facing slopes tend to sultry slower than south-facing slopes. Warm-season grass can be sown well into summer, as seeds germinate in soil between 65° to 95° F. Sowing too delayed in the summer can expose seedlings to icy temperatures before they have time to fully establish. Seed warm-season grasses at least 90 days before the average fall frost date to allow plants time to establish before winter.

Cool-season grasses establish best when soil begins to sultry but air temperatures are still moderate. Record soil temperatures regularly in early- to mid-spring and sow grass seed when soil temperatures consistently measure between 50° and 65°F. Correlating air temperatures will range between 60 to 85°F. Avoid sowing grass seed into icy, saturated soil which can limit germination and lead to disease challenges.

For homeowners in the Northeast and Midwest, spring temperatures are quite conducive to growing cool-season grasses (which are the only type grown here). April tends to be the ideal time for spring-sowing of grass seed in these regions, as soil and air temperatures reach their ideal ranges. Rains are also plentiful during spring, which can benefit establishment. However, these conditions also favor weeds, particularly crabgrass. Weeds pose a significant challenge to establishing cool-season lawns in spring, as discussed below.

While spring sowing is an option, fall is the best time to seed cool-season grasses, no matter where you live. Fall-sowing gives plants more time to establish before the heat of summer sets in and shuts
down vigorous growth.

Challenges Of Spring Planting

One of the greatest challenges of planting grass seeds in spring is competition from weeds. Warm soil and bountiful rainfall favor weeds as much as they do grasses, leading to significant competition for water and nutrients, not to mention an unsightly lawn. Starting with a weed-free planting bed is your best defense against weeds. In spring-sown turf areas, hand weeding will play an vital role in weed management.

Pre-emergent herbicides are commonly applied to lawns in early spring to manage crabgrass and other weeds, but these cannot be used in areas where grass seed is sown because they also prevent grass seeds from germinating. They remain vigorous for up to 90 days, so adjusting planting times does not support avoid problems with pre-emergent herbicides.

There are some products available (e.g. Dithiopyr) that can be applied after grass seed germinates yet still provides good control of crabgrass, however these are toxic to bees, fish, and aquatic insects. Waiting until fall to sow grass offers a simpler and safer solution. It also allows you time to manage weeds during the growing season leading up to fall planting. And pre or post-emergent herbicides can be applied the following spring, as grasses are already established.

Summer heat and drought can take their toll on juvenile turf areas. Keeping lawns properly watered helps manage water stress in establishing lawns. Cool-season grasses are particularly vulnerable during the summer months, as they are not actively growing. Fall planting gives cool-season grasses a much longer period of time to establish a well root system before the heat of summer arrives.

Unpredictable spring weather can make lawn establishment a challenge. Using a soil thermometer to monitor soil temperature and keeping track of air temperatures can support you identify the ideal time to plant. Also pay attention to weather forecasts. Avoid planting grass seed right before weighty rainstorms, which can wash seeds away.  

Alternatives And Additional Tips

While spring is the best time to plant warm-season grasses, consider fall as an alternative for cool-season grass species. Soils hold summer heat well into autumn, providing the warmth seeds need to germinate. At the same time, air temperatures are more moderate and rains often plentiful. Plant roots grow if soil temperatures remain over 40°F, which means turf grasses will continue to establish a well root system through much of fall and early spring (and even during the winter months in Southern landscapes).  

To make the most of spring planting, start with site preparation and careful plant selection. Identify the best type of turf grass for your planting site based on local climate and specific site conditions such as sun exposure, soil type, and access to irrigation. Prepare the planting bed by removing existing weeds, rocks, and other debris and raking the surface glossy. Conduct a soil test and amend soil accordingly. Purchase high-quality, weed-free seed and sow at the recommended rate for full coverage. Keep the seeded area saturated through daily, airy waterings for the first two weeks as seedlings emerge, then reduce the frequency of watering and practice deeper irrigation.

Grass seeds can be broadcast over an existing lawn to thicken stands that have thinned out or to fill bare patches. This is called overseeding and is commonly practiced on cool-season lawns. Overseed in the fall (ideally) or spring. Start by cutting the lawn very low and raking the planting area to remove the clippings, dead grass, and other debris. Raking also loosens the soil which will provide better seed-to-soil contact. Consider spreading a very lean (¼-inch hefty) layer of topsoil across the planting area before sowing seed according to label instructions.

Frequently Asked Questions

• What is the best month to plant grass seed in spring?

  There is no one best time to sow grass seed, as local weather patterns greatly impact soil temperature and different grass species have unique needs. In general, warm-season grasses, which grow actively during the warmer months, are sown between April and June. Cool-season grasses grow actively during fall and spring. Soil temperate dictates the best time to seed cool-season grasses in spring, which generally falls between April and May, depending on location.

• How can I prevent weeds when planting grass seed in spring?

  Weeds are very arduous to manage when seeding a novel lawn. Weed seeds benefit from the same growing conditions as grass seeds. Pre- and post-emergent herbicides traditionally used to manage lawn weeds cannot be used in areas that are to be seeded or where grass was recently seeded. As much as possible, start with a weed-free planting bed by physically removing existing plant material. Weed seed beds are often bountiful and novel weed seeds are likely to germinate, even in the best prepared beds, particularly if they are tilled. Your best defense against weeds is regular hand removal until grasses are established.

• What are the advantages of planting grass seed in the fall instead of spring?

  Only cool-season grasses such as fescues, Kentucky bluegrass, and ryegrasses can be planted in fall, which is the best time of year to establish these species. Soil and air temperatures are ideal during the fall months, with soil still sultry from the summer and cooler air temperatures placing less stress on juvenile plants. Fall planting provides lawns a longer window of time to establish before the stressful heat of summer sets in. These established plants are then better able to compete against spring weeds, and the timing allows for operate of conventional weed management strategies that cannot be used in spring-sown turf areas.