How to Fix a Weedy & Patchy Lawn
Work a little, water a lot — and then enjoy!
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IntroductionReseeding is a job you can do in a weekend if you have an average-sized lawn. You’ll have to wrestle home a couple of engine-powered rental machines. And once your work is done, be prepared to keep the soil damp with daily watering for the first month or so. It’s the key to a successful reseeding job.
- Aerator (Rental)
- Broadcast spreader
- Power Rake (Rental)
Can You Save the Existing Grass?
The steps we show here are for a lawn that’s at least 50 percent grass.
Take a close look at the lawn. If you see plenty of healthy grass among the weeds or large areas of good grass throughout the lawn, you can save the existing grass and fill in the rest by planting new seed. That calls for applying a broadleaf herbicide, which kills the weeds without harming the grass. It should be applied three to four weeks before starting the project. A hose-end sprayer with concentrated weed killer is the fastest and easiest application method (photo with Step 1).
But if your lawn is hopelessly bare or completely covered with weeds, it’s best to go “scorched earth” and kill all the vegetation with a nonselective herbicide and start over. If after two weeks some weeds reappear, apply another treatment.
Project step-by-step (10)
Reseeding can be a crapshoot. A big thunderstorm could wash your seed away, so pay attention to long-range forecasts and plan accordingly. That’s especially true if your yard is sloped enough that it doesn’t take much water to wash away seed.
- Before you start the soil prep, set your mower to its lowest setting and give your yard a buzz cut.
Kill the Weeds
- Use a hose-end sprayer to spray the lawn with a broadleaf weed killer at least three weeks before you plant the new grass seed.
- Wear eye protection, gloves, a long-sleeve shirt, long pants and waterproof shoes.
Aerate the Soil
Aerators pull small plugs from the soil and deposit them on the surface. That loosens the soil, making it easier for roots to grow deep into the soil. The plugs will be pulverized in the next step — power raking — to form loose soil for the seeds to germinate in. The holes you create will allow fertilizer and water to penetrate deep into the soil for better retention.
- When you’re using a core aerator to prepare soil for reseeding, the key is to make at least three passes — more if you have the stamina — each from a different direction.
Prepare the Surface
Power rakes spin metal tines at high speed to scarify and loosen the soil as well as break up the aerator plugs. They also lift thatch from your lawn.
- Go over the whole lawn from two directions.
- Rake up and remove dead debris if it completely covers the ground and might prevent seed from contacting the soil.
Outline Garden Beds
In most cases, a broadcast spreader is the best choice because it evenly distributes seed or fertilizer for thorough coverage. If you have a large yard bordered by flower beds or vegetable gardens, use a drop spreader to spread the seed near them before doing the majority of the yard with a broadcast spreader. Since the seed drops straight down, you won’t be casting grass seed in your gardens by mistake.
- Whichever spreader you use, set the feed rate at half (or less) of the recommended rate.
- When using the drop spreader around border gardens, overlap subsequent passes slightly for more even seed distribution.
Seed the Large Areas
- Spread seed with a broadcast spreader in large areas away from gardens. Use half the recommended drop rate to spread the seed in one direction.
- Pro tip: When using the broadcast or drop spreader for the open areas, make two or more passes from different directions for even distribution. This is especially true when you’re using a drop spreader so you don’t wind up with a striped lawn. If you don’t own a broadcast spreader, buy one — don’t rent it. You’ll need it to keep your new lawn in tip-top shape after it’s established.
Rake in the Seed
- Applying too much or too little seed is a mistake.
- Pro tip: Picture a square inch of area on a freshly-seeded area and count the seeds. Aim for about 15 or so seeds per square inch.
- After spreading, lightly rake the seed into the soil for good contact. It doesn’t have to be completely buried. Some of the seed can still be showing.
Distribute the Fertilizer
Fertilizers used to contain nitrogen, phosphorus and potassium. But due to water pollution concerns, many states no longer allow phosphorus in ordinary lawn fertilizers. However, phosphorus is helpful for root development, so it’s important for starting new seed.
- At the garden center, look for fertilizer labeled “Starter” or “New Lawns.” Your state may allow its sale for establishing new lawns or in gardens.
- Spread starter fertilizer over the yard. Follow the directions on the bag to determine how many pounds per 1,000 sq. ft.
An oscillating sprinkler works best for getting your lawn started. It covers a large area with even, light streams of water to prevent washing away seed. You’ll only need to water for about 20 minutes at a time depending on your soil type. Unless it rains, you’ll likely need to water at least twice daily. On hot or windy days, you may need to water even more frequently.
- Closely monitor the soil to keep it damp, not saturated. Strive to maintain soil dampness to a depth of about 1/2-in. You’ll need to do this for at least three weeks. If you’re not diligent, you may throw away all your hard work and money. One dry, hot sunny day is all it takes to wipe out a new lawn.
- Pro tip: A $25 timer for your hose, available at any garden or home center, might be helpful if you can’t be home to water as needed. After the grass is three inches high, you can start mowing and begin a normal watering regime.
Soil Watering Gauge
Your goal should be to water to a depth of 1/2-in.
- As a test, water for about 20 minutes, then drive a spade into the ground and look for the dark line near the surface indicating water penetration. That will tell you if you should water for longer or shorter periods.