How to Care for New Grass Seed: Watering, Mowing and the First Six Weeks

Overseeding is the best thing a tall fescue lawn gets all year, but the seed is only half the job. What happens in the next six weeks decides how much of it comes up and how thick your lawn looks next spring. Here's what I tell my customers after every fall overseeding.

Weeks 1–3: keep the seed moist

Tall fescue usually sprouts in 7 to 14 days when the soil is warm, a little longer if the weather turns cool. Until it does, the seed has to stay moist. If it dries out after it has started to sprout, it dies.

• Water lightly once or twice a day, enough to keep the top half inch of soil damp. Short cycles are better than one long soak, which can wash seed into puddles.
• Skip watering on days it rains, and back off if water is pooling or running off.
• Morning is the best time. If you water a second time, early afternoon is better than evening, so the grass dries before night.
• If you have a sprinkler system, short cycles on each zone work well. Check that every seeded area actually gets wet, especially along edges and slopes.

Weeks 3–6: water less often, but deeper

Once most of the seed is up and the new grass is an inch or two tall, start stretching it out: water every other day, then every few days, but longer each time. That pushes the roots deeper, which is what gets the lawn through winter and next summer. Not sure whether it has rained enough? Check this week's watering numbers for Raleigh, updated daily.

The first mowing

• Wait until the new grass is about 4 inches tall. For most lawns that's 3 to 4 weeks after seeding.
• Mow to about 3 inches, taking off no more than a third of the blade.
• Use a sharp blade and mow when the grass is dry. A dull blade or wet grass can rip seedlings out by the roots.
• Bag or mulch? Either is fine. Just don't leave clumps sitting on the new grass.

Keep traffic and leaves off

New grass doesn't like being walked on. Keep foot traffic, kids' play and pets off the seeded areas as much as you can for the first few weeks. And when the leaves start falling, don't let them sit on the new grass. I'll cover leaves and new grass in next week's post, because it's the number one way fall seedings fail.

Don't put down weed killer or weed-and-feed

Most weed killers and weed-and-feed products can damage or kill new seedlings, and many crabgrass preventers stop grass seed from sprouting at all. If you're on one of my programs, I handle the timing and only use products that are safe on new grass. If you see weeds coming up with the new grass, don't worry: a lot of them are summer annuals that will die off with the first frost, and the rest I'll take care of when it's safe.

Feeding

New grass needs fuel. I put down a starter fertilizer a couple of weeks after seeding to feed the young roots, followed by fall feedings into November. That's the stretch when fescue does its real growing, and it's why fall-seeded lawns look so much better by spring.

What to expect

• Weeks 1–2: a fine green fuzz, thickest in the aeration holes.
• Weeks 3–6: it fills in and looks like a lawn. Some spots will be thicker than others.
• Spring: the real payoff. Fall-seeded fescue has had all winter to root in and comes back thick and green.

A few thin spots are normal, especially in shade. If you're on my Premium program, reseeding thin spots is included. Questions about your lawn? Send me a photo through the free photo checkup.

About the author: David is the owner-operator of Thriving Lawns and an NC-licensed pesticide applicator caring for lawns across North Raleigh and southeast Durham. Get a free estimate →