How Late in the Year Can You Plant Grass Seed?

Did you think that the best time for planting everything is in spring? Surprise! Grass seed, for one, has a much better chance for survival if you wait until early fall. Read on to learn why, plus pro tips for successful fall grass planting.

Note: Seeding times vary depending upon where you live. Content expressed here reflects recommendations for Northern lawns (north of Interstate 70) when seeding cool-season grasses, like Kentucky bluegrass, fine fescue and perennial ryegrass. Timing will vary by several days or even weeks with the arrival of winter being different in each region.

Why Plant Grass Seed in the Fall?

Late summer and early fall are the best times to reseed your lawn or to establish a new one.

• Soil temperature: During this time soil temperatures are warm enough to trigger instant seed germination. Spring soil can still be too cold to get seeds to germinate. This is why seeding a lawn in the spring is generally not a good idea. Seeds can rot if they lay in cold soil for weeks without germinating. Grass seed germinates and establishes quickly when late summer and early fall soil temperatures are in the upper 60s or low 70s F.
• Air temperature: Ambient temperatures are important, too. By late summer, nighttime air temperatures begin to cool. This gives new seedlings a break from warmer daytime temperatures that are equally important to promote shoot and root growth as photosynthesis production is in high gear. Cool nighttime conditions also help minimize disease activity that can completely wipe out tender new sprouts in just hours.
• Weeds: Weed competition is extremely low toward the end of the growing season, too. In spring, it seems every weed seed in your lawn is popping out of the ground. These newly sprouted weeds compete with new grass seedlings for water, sunlight and space. They usually grow quicker than lawn seed, so they can easily smother new seedlings and prevent them from establishing. By late summer and early fall, lawn weeds, like crabgrass, have quit growing. This gives your lawn seed a better chance to find the space, water and nutrients to sprout and grow.

How Late Can You Plant Grass Seed?

This will depend on where you live. The farther south you live, the later you can sow grass seed. If you live near the Canadian border, you’ll be seeding a good six to eight weeks earlier than you would in Kansas City. The trick is to give your new seedlings plenty of time to germinate, establish and mature before harsh winter weather arrives. If you wait too long, the first hard frost could severely damage or kill tender new seedlings that have just emerged from the soil. A good rule of thumb is to have mowed your newly seeded lawn at least twice before winter weather takes its grip. Like the rest of your lawn, new grass seedlings need to go dormant and harden off before the ground freezes and the snow arrives.

For example, if you live in Chicago, where the first hard frost generally occurs around Oct. 25, you would be wise to have your lawn seeded by September 15. This will give those new seeds adequate time to germinate, establish and be mowed a couple of times before Old Man Winter arrives. The entire process from seeding to a second mowing could be as long as eight weeks, so plan ahead!

Waiting too late will not allow new seedlings to properly establish and mature and this can create a situation where you’ll be tempted to reseed again in the spring when conditions are less than perfect.

Top Seeding Tips for Planting Grass in Fall

• Research your seed mixture options. Typically the higher the price the better the seed. This is not the time to skimp.
• Prepare the soil before sowing the seed. Loosen the soil by scratching the surface lightly with a garden tool or bow rake.
• Sow the recommended amount of seed, apply a quality starter fertilizer and gently scratch both into the top one-quarter inch of soil. No deeper.
• Keep the newly seeded area moist during seedling establishment and four to six weeks after. This will ensure those tender new seedlings grow into a thick, healthy turf.
• Apply a second application of starter fertilizer 30 to 45 days after seeding.

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