A Beginner’s Guide to Reseeding a Lawn With Grass Seed

Reseeding a lawn with new grass seed can serve several purposes. New seed can rehabilitate a thinning lawn or prevent thinning in the first place, it can fill in bare spots and it can bring renewed life to the yard after removal of an old lawn. In the South, reseeding with a cool-season grass in the fall can help the lawn maintain its green color while the existing warm-season grass snoozes for the winter.

The type of grass you should use depends on the reason you're reseeding as well as your climate zone and the characteristics of your property. If you're overseeding an existing lawn, you'll want a grass variety that can coexist with the existing grass and hopefully improve it, but if you're reseeding after lawn removal, you'll be looking for a variety or mixture that can stand on its own. You'll find a lot of varieties, blends and mixtures out there, and it doesn't hurt to consult with a landscaper or garden center to help you make the best choice.

Like a favorite wool sweater with too many holes, an old lawn with thinning or dead grass, bare spots and weeds may have served its usefulness and may need to be replaced with something new. Once you've made the decision to remove it, there are four strategies, and two of them can take several months, so you may need to plan ahead.

• ​Solarizing​ involves covering the existing grass with clear plastic and letting the sun fricassee it, after which you can turn it into the soil to serve as compost for the new grass.
• ​Layering​ is a strategy by which you cover the grass with layers of newspaper or cardboard followed by a layer of compost and a layer of organic mulch.
• ​Chemical dispatch​ of the old grass can be accomplished with an herbicide such as glyphosate, but it's probably safer for the soil and the groundwater to use vinegar. You may have to apply it several times to finish the job.
• ​Manual removal​ with a sod cutter is the quickest and most labor-intensive approach, allowing you to complete removal and reseeding in a matter of days rather than months.

If you use a gradual lawn removal method like solarization or layering, you should begin the process four to six months before the date you plan to reseed, which is typically in the spring for warm-season grasses and in the fall for cool-season ones.

Whether you're replanting a lawn that you've removed or you're reseeding existing grass, it's important to test the soil and make amendments to ensure the new grass gets off to a good start. Ideally, the pH should be close to a neutral 7.0, but the soil may be acidic, particularly if you used vinegar to remove the previous lawn. You can rectify this with lime.

If the soil is already alkaline, it probably lacks nutrients as well, and you can address both problems by working in some compost in addition to any starter fertilizer you use when you sow the seed. Grasses need both nitrogen for the blades and phosphorous for the roots, so most grass fertilizers have one or both of these nutrients in abundance.

Some grass varieties grow in warm climates, some grow in colder climates and some are best for transition zones that occur throughout the central part of the country, along the West Coast and in microclimates. You usually want to choose a seed that is appropriate for your region but not always. For example, landscapers in the South sometimes overseed with a cool-season grass in fall to keep the lawn green throughout the winter when the existing grass goes dormant, and it's common to use a variety outside its climatic comfort zone in a location that is particularly sunny or shady.

When you're repairing an existing lawn, a seed mix is often the best option. Mixes typically contain seeds blended to capitalize on their various abilities to grow quickly, crowd out weeds, resist drought and produce a thick texture. For example, Pennington Smart Seed Sun and Shade contains several varieties of tall and fine fescue rounded out with Kentucky bluegrass to create a fine-bladed, dark-green lawn that grows quickly even in drought conditions. Scotts PatchMaster is a lawn-repair mix that incorporates pelletized paper mulch to absorb water and keep the seeds healthy while they germinate and take root.

If you removed an old lawn, you'll want to turn the soil to a depth of 2 to 3 inches, working in any soil amendments that are needed and removing clumps larger than the size of a half dollar. Use a rake to level the soil and fill in any low spots where water can collect. If you haven't yet installed a sprinkler system, this is the best time to do it.

When overseeding an existing lawn, begin by mowing it as short as possible and removing the grass clippings to ensure the seed makes good contact with the ground. Aeration is important, especially if the soil is clay, and a core aerator is the best tool for this project. Spread seed-starting fertilizer unless you're using a seed mix that includes a fertilizer, such as PatchMaster.

If you live in a warm climate, the best time for sowing seed for a new lawn is late spring so the seed can take advantage of the peak summer growing season, but if you're in a cool climate, plant in late summer or early fall at least 45 days before the first fall frost. You can use a hand spreader, a broadcast spreader or if you're reseeding a small area, you can do it by hand. When using a spreader, you can set it to deliver seed at the rate recommended on the seed package, but when doing it by hand, you may have to estimate.

An easy way to estimate is to weigh out the recommended amount for a certain coverage area, hold it in your hand to get a feel for it and then spread approximately the same amount over the same area until the lawn is seeded. If you're only spreading seed on bare patches, you can purchase a container with holes and shake out the seed as if you were shaking salt.

Birds will be interested in the seed, and to protect it, it's usually a good idea to spread a fine layer of soil over the lawn after seeding, combining this with a 21-22-4, 30-0-4 or 12-22-8 seed-starting fertilizer depending on the soil characteristics and the type of seed you're planting. Always use fertilizer at the rate recommended on the label. Mist the new lawn immediately after sowing the seed and keep the ground moist until the seed has germinated and the new grass is established.