5 Simple Steps to Overseeding a Lawn
Is your lawn looking less lush than you'd like? Overseeding, which chokes out weeds and fills in bare patches on your property, may be the solution you're looking for.
A full, green lawn creates curb appeal and makes you feel like sipping an iced tea on the back patio. But if bare spots peek through and weeds overpower the grass, the lawn might be more of an eyesore than a point of pride. Overseeding chokes weeds and fills out the grass until it’s thick and lush. If you’re not sure how to overseed a lawn, all it takes is the right tools, smart timing, and a little knowledge about your local climate.
What does “overseeding” mean, exactly—why is this lawn task not just called “seeding”? “Overseeding” the term for adding more grass seed to a lawn without turning the topsoil. For many homeowners, overseeding is part of general lawn maintenance. Some lawns might need overseeding once a year if drought or disease threaten the grass, and other lawns might need it every few years only to brighten the grass and keep it full.
A few basic tools—like a lawn mower, seed and fertilizer spreader, and rake—are all that’s needed to achieve a less patchy, more verdant yard. With the right grass seed and timing, overseeding will restore the lawn and make it hard to resist spending the day lounging in the yard.
Note: If your lawn has thatch (a compact layer of grass and soil), it might need dethatching or aerating before you spread seed. Otherwise, the grass seed used in overseeding won’t reach the soil to germinate and take root. Aerating creates holes in the grass and soil through which water, oxygen, and vital nutrients can reach the new grass seed and the roots of the existing grass.
STEP 1: Mow and rake the lawn.
The goal of overseeding a lawn is to get the grass seed in contact with the soil. To do that, the first step is to mow the lawn. Mow it shorter than usual so the grass seed will have a better chance of reaching the soil. Make sure to bag the clippings so they don’t come between the seeds and soil.
After mowing, rake the entire lawn to remove dead grass, rocks, sticks, and any other debris. This process removes any final barriers between the grass seed and soil, and loosens the soil in preparation for seeding and germination.
STEP 2: Amend the soil.
Soil amendments are different from fertilizers in that amendments have specific nutrients and chemical compositions for specific soil types. For example, lime, wood ash, and poultry manure raise the pH level of acidic soil to make it more suitable for certain plants and grasses. Sulfur amendments, on the other hand, add acidity to alkaline soil. Additions of peat moss for clay soil and compost for sandy soil also can improve the nutrients in the lawn and its condition.
If a lawn has not been growing and greening as it should, doing a soil test can determine the soil type and pH. The test results will identify what, if any, types of amendments the soil needs for grass to develop. Keep in mind that if the soil has a neutral pH and is fertile, it likely needs no amendments.
STEP 3: Spread the grass seed.
At the appropriate time to overseed (knowing when to reseed a lawn is based on your climate and grass type), start by loading the grass seed into a seed spreader and spread about 16 seeds per square inch of soil. The right seed density will depend on the thickness of the existing lawn, so some lawns might need less. You also can spread grass seed by hand if you don’t have a spreader.
Choose a grass seed designed for your climate or region and that complements the existing grass. Lawns with cool-season grasses thrive in variable temperatures like those found in the Northeast and Pacific Northwest. Warm-season grasses grow best in a climate like that of the southern United States.
Consulting the USDA Plant Hardiness Zone Map can help determine the average local climate to best choose the appropriate grass type. Look for grass seed that’s rated by the National Turfgrass Evaluation Program because these varieties have been tested and found resistant to disease, drought, and common pests.
STEP 4: Add grass seed fertilizer.
Select the best fertilizer, and load it into a fertilizer spreader. Then, scatter around the perimeter of the lawn first to make sure fertilizer reaches the edges. Next, follow a pattern similar to a mowing pattern by moving in straight rows until the entire lawn is fertilized.
There are different types of fertilizer spreaders, including a broadcast spreader, handheld spreader, snap spreader, drop spreader, and liquid sprayer. Fertilizing small yards often requires a small handheld spreader only, while larger yards will take less time and effort with a broadcast spreader.
Both yard size and fertilizer type will determine which type of spreader is best for your property. For example, liquid fertilizer is applied via sprayer, like one of these quality backpack sprayers, and midsize yards are more easily fertilized with a snap or drop spreader. Keep in mind that some spreaders can handle both grass seed and fertilizer broadcasting, so depending on the fertilizer type and spreader, you might only need one tool for both steps.
STEP 5: Water the seeded lawn.
After fertilizing, water the lawn for a short time each day. It’s best to water in the morning to maximize the water intake. More evaporation occurs during the afternoon and evening, which means it will take more water to get the same benefits. You don’t want to overwater the lawn because doing so can wash away the seed, prevent germination, or encourage thatch development and the growth of fungus and weeds. If there are puddles or the ground feels spongy, cut back on the watering time.
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Part of learning how to overseed a lawn requires knowing when to do it, and this has everything to do with climate and grass type. Cool-season grasses seed best in the late summer and early fall. The cooler temperatures slow the growth of the existing grass but give the seeds time to germinate and grow before the grass goes dormant. Warm-season grass does best when seeded between early spring and early summer. In this case, the seed has time to germinate and grow before the warmest summer temperatures hit.
This method of overseeding should successfully fill in the lawn with lush, green growth. Remember to choose a grass seed intended for your climate, and perform a soil test to determine whether the lawn needs any extra nutrients to germinate and thrive. Finally, water the lawn for a short time each day and don’t mow until the new grass reaches 1 to 2 inches tall.
Overseeding lawn grass is not a tough project to complete, especially if you follow the steps and use the tools outlined above. Begin by choosing the best time for success based on your growing region and grass type (cool or warm season). Then, prep the area for lawn seeding by mowing and raking. If the lawn has a thick layer of thatch, use a thatch rake or aerate the lawn before seeding. Then, move on to amending the soil as needed to make sure your grass seed will root and grow to create a healthy, lush lawn.
Select a seed based on the existing grass and climate or other conditions, then spread it by hand or with a spreader. Next, add some fertilizer, broadcasting it evenly with a spreader. Then, water the lawn and keep it regularly moist but not so wet that water runs or puddles.
FAQs About Overseeding Lawns
Not every lawn is the same, and you might still have questions about when or how to overseed existing grass. Below, we answer some common questions.
Q. Can you just sprinkle grass seed on lawns?
You will have very little success overseeding a lawn if you just head out and sprinkle grass seed and then cross your fingers. For grass seed to take, the soil must be ready and free of barriers like grass clippings. If the lawn has lots of weeds that compete with grass, for example, sprinkling seed is a waste of time.
Be diligent and first take the appropriate steps to prepare the soil. After all, the fact that you need to reseed might mean that your yard has thatch or other issues that should be addressed first.
Q. When is the best time to overseed a lawn?
Knowing when to overseed a lawn depends largely on grass type. Sow cool-season grass seed in late summer and early fall, giving the seedlings a little time to develop before winter. Overseed a warm-season lawn in spring for best success. Also, try not to overseed on especially windy days or after a heavy rain.
Q. What do you put down first, grass seed or fertilizer?
First, spread your seed on prepared soil, then add grass seed fertilizer. Since you typically are overseeding in fall or late summer for cool-season grasses, and in spring for warm-season ones, you might as well apply your fertilizer to the entire lawn anyway, not just the overseeded portions. It’s typical to seed and fertilize a lawn at the beginning of the turf’s growing season.
Q. How long after overseeding can I mow?
Mowing after overseeding a lawn requires a little patience. You might be itching to make your lusher lawn a nice, even carpet of turf now that it has filled in. But you should wait until the new grass blades are about 2 inches tall. Since you mowed as part of preparing the soil for lawn seeding, the established grass shouldn’t be wildly overgrown.