Lawns: How to Reseed

How to kill off the old grass and seed a healthy new lawn

Create a healthy lawn by starting over

Let's get this straight right from the get-go: A healthy lawn doesn't get taken over by weeds. So if it looks like you're raising weeds instead of grass, that's a sign of a more serious problem. And that may mean killing off the grass and starting over. It's a big project that'll take several weekends and may cost you up to 25¢ per sq. ft. for equipment rentals, soil conditioners and seed. If you're willing to spend more, you can lay sod instead of planting seed, but don't skip the soil testing and remediation steps.

Are you ready for a fresh start? Just follow our guide and you'll be the happiest gnomeowner on your block.

Evaluate Your Lawn

Going “nuclear” shouldn't be your first option. Instead, start with spot applications of weed killer, dethatching and core aeration. But if you still see more than 60 percent weeds at the start of the next growing season, your lawn is too far gone to save. Your best option is to nuke it and replant.

Note: To find out how to dethatch and aerate for greener, healthier grass, search for “lawn.”

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Step 1: Get a soil analysis

Don't even think about replanting until you get the results of a soil analysis (cost is usually less than $20). Contact a local extension service or search the Internet for a soil-testing lab near you. Select three different locations around your lawn and collect samples. Mix them together and scoop into a container. Note on the lab form that you'll be planting new grass and whether you bag the clippings when you mow or return them to the lawn. In a couple of weeks, you'll get a report with recommendations about which fertilizers or soil treatments to add.

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Step 2: Kill everything

You can kill the grass with chemicals like Roundup or Killzall. But if you hate the idea of using chemicals and have a large area, rent a sod cutter to remove the lawn surface. Or kill the grass by blocking out its sunlight with black poly film (4-mil or thicker; about $100 for a 28-ft. x 100-ft. roll). Remove the poly when the grass is dry and brown (two to three weeks or longer, depending on the weather).

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Step 3: Remove the dead stuff

Now comes the upper body workout: Rake up the dead grass and weeds before you amend the soil. Yup, it's got to be done.

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Step 4: Improve the soil

Don't think you can fix bad soil just by adding a few inches of black soil on top of the old. Instead, rent a tiller (about $45 per day) to till in the soil conditioners recommended by the soil analysis.

“Adding good-quality black topsoil over bad soil is like putting chocolate frosting on a stale cake—it doesn't fix the underlying problem.”
Bob Mugaas, Turf Expert

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Step 5: Smooth the soil

Grass seed needs smooth and level ground to get the best germination. And it needs good seed-to-soil contact. So first remove all rocks and debris, then smooth the soil with a rake.

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Step 6: Add a starter fertilizer

A starter fertilizer gives grass seed the nutrients it needs to germinate and grow quickly. Consult with a local nursery to find the best starter fertilizer for the seed you select. Follow the instructions on the bag for the proper spread rate for a new lawn and apply the fertilizer.

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Step 7: Pick seed to match your site

Consult with the grass expert at a garden center to select a seed that matches your site conditions, lawn care preferences and budget. Ask about the newer low-maintenance and drought-resistant varieties. Purchase grass seed by the bag or in bulk, by the pound. But buy just what you need. Don't apply the leftover seed—extra seed actually reduces the germination rate.

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Step 8: Prepare the seed

To avoid applying too much seed, mix the seed (4:1 ratio) with a fertilizer/ bulking agent (Milorganite is one brand; about $15 for a 36-lb. bag).

When to Plant

There are good and bad times of year for starting a project like this. in cold climates, plant new grass seed in early spring as the lawns are just coming out of winter (early to mid-April) or late summer from about mid-august to mid-September. in warm-weather climates, plant in late spring/early summer. if you're not sure, contact your local extension service to get planting advice from a turf expert.

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Step 9: Spread the seed

Load the seed into a spreader and apply it. Make sure it doesn't fly into nearby gardens. Rake to cover the furrows as shown. Then compact the soil with a sod roller (rent one for about $20 per day) to get good seed-to-soil contact.

Note: To learn how to use a spreader fertilizer and reseed your lawn, search for “fertilizer.”

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Step 10: Add mulch or grass seed accelerator

Cover the soil with compost mulch to retain water during germination. Or apply a “grass seed accelerator” (one brand is GreenView, greenviewfertilizer.com; about $22 for 30 lbs., which covers 600 sq. ft.). The accelerator absorbs more moisture than either mulch or hay and then slowly releases it. It also degrades naturally, eliminating cleanup.

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Step 11: Water, but not too much

Water the new lawn generously right after the mulch application, but stop as soon as you see puddles forming. Then keep the soil moist to a depth of 4 to 6 in. for best germination. Keep watering regularly as the seedlings appear and grow. Gradually reduce the watering over a six-week period. Then switch to your normal watering routine.

“Most people overwater new seed. Just keep the soil damp for the best germination.”
Bob Mugaas, Turf Expert

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Step 12: Cut the grass with TLC

Set the cutting height to 2-1/2 in. Use a new or sharpened blade to make sharp, clean slicing cuts. Avoid using a dull blade—it rips the grass, setting up the conditions for disease.

Note: Find out how to sharpen a lawn mower blade. Search for “sharpen blade.”

Meet Our Grass Guru

Bob Mugaas is an Extension Educator in Horticulture with the University of Minnesota Extension. Bob has authored or co-authored more than 200 articles on various topics related to turf grass management.

Bob Mugaas
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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Garden rake
  • Broom rake

You'll also need a shovel, power tiller, spreader, sod roller, sprinkler and lawn mower.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Black plastic or herbicide
  • Soil conditioners
  • Lawn starter fertilizer
  • Grass seed
  • Seed accelerator