How to Patch and Rehabilitate Your Lawn

By Joe Lamp’l - Gardening Expert and Host of Growing a Greener World®
September 2, 2023

Sooner or later, even the best-maintained lawn will develop bare spots that require rehabilitation. In this post, I’ll explain the simple steps to patching a lawn for quality, healthy turf.

There are many reasons for dead spots in lawns — from foot traffic and dogs relieving themselves to herbicide and fertilizer spills — but no matter the cause, you can use the following steps to regrow grass in those troubled areas and restore the lawn’s vigor.

Step 1: Get a Soil Test

If your lawn is not looking as nice as it once did, the problem could be your soil, or more specifically, a lack of nutrients in your soil. The big question is, what nutrients are missing? Finding out the answer starts with contacting your county cooperative extension and asking for a soil test kit for both a pH test and a nutrient analysis. Extension agents will explain how to collect soil samples, package them, and mail them to the lab. It will only cost you $20 or so, but the information will be invaluable for improving your lawn.

The lab will send you a report detailing the nutritional requirements your soil needs to promote optimal lawn growth. The most important information to note will be the pH and the levels of nitrogen, phosphorus and potassium — the three macronutrients. The report will provide instructions for getting the pH and nutrients into balance by applying the appropriate amount of lime and fertilizer. Simply follow their instructions, and you’re well on your way.

Step 2: Identify What Kind of Grass You Have

Not all turf grass is the same, and the most important distinction to understand is the difference between cool-season and warm-season grasses

Cool-season grasses are adapted to climates with cold winters, so if you live in the northern United States, these are the grasses for you. A few popular examples are Kentucky bluegrass, fescue and winter ryegrass.

A northern lawn made up of cool-season grasses looks its best in spring and fall. In summer, cool-season grasses grow slowly, and newly sown seeds won’t have time to establish the roots they need to tolerate heat and drought. The best times to patch a cool-season lawn are in March and April or in September. Fall is your best bet because the new grass will have all fall, winter and spring to get established before the summer heat sets in.

Warm-season grasses, such as Bermuda, centipedegrass, St. Augustine, and Zoysia, are best suited to southern lawns and stay green in summer because they can tolerate the heat. The downside is they turn brown and go dormant in winter — though they come roaring back again in spring.

Put down warm-season grass seed in late spring or early summer once the soil temperature exceeds 65°. Take a soil temperature reading at a depth of three inches to be sure the soil is warm enough.

Before buying a bag of grass seed, make sure it will be compatible with your lawn. The best garden centers sell local mixes that are a blend of grass species selected specifically for your area’s climate and soil type. There are also sun mixes and shade mixes.

Step 3: Remove Weeds

Thick turf leaves little room and opportunity for weeds to take hold, but when turf is thin and spotty, it’s easy for weeds to get established. Getting those weeds out of there is necessary before putting down grass seed. Otherwise, the weeds will easily out-compete the sprouting grass for nutrients, moisture and space.

If you practice organic lawn care like me, you can remove weeds with a long-handled weeder — which is much easier on the knees and back than crouching down to pull weeds by hand. There are numerous designs for weeding tools that scrape up, pull, or cut weeds. You’ll find at least one design you really enjoy using.

Step 4: Dethatch

Thatch is a build-up of dead grass blades and roots, plus other organic debris, that does not readily decompose. Water and fertilizer have trouble penetrating the thatch layer, and thatch can also be a barrier that prevents grass seeds from making soil contact and sprouting.

Dethaching can be done with a typical bow rake or with a thatch rake made specifically for detaching lawns. You can also rent or buy a power dethatcher that you can push around like a lawn mower.

Overwatering and using chemical fertilizers contribute to thatch buildup. Ideally, your lawn will have a half-inch of thatch to help maintain the moisture level and soil temperature. Any more is too much.

Step 5: Aerate

An aerator is a machine available for rent that extracts cores of thatch and soil from the lawn. Aerating the lawn will reduce soil compaction, improve drainage and encourage root expansion, while also making it easier for fertilizer and oxygen to reach the roots of the grass and for seeds to make the soil contact they require to germinate. 

The best time to aerate is right after a soaking rain, when the ground is softer and core extraction is easier.

Step 6: Apply Soil Amendments

If your soil test results call for raising the pH of the soil by adding lime, the best time to do so is right after aeration. Compost and other recommended soil amendments should also be applied at this time when the openings created by the aerator haven’t closed up yet.

Applying compost will help sandy soil retain moisture better and will help clay soil to drain better. Compost also encourages beneficial microbes that help grassroots access the nutrients in the soil. It can really make a difference in your lawn’s vitality.

Step 7: Apply Organic Fertilizer

I always supplement organic amendments with a non-burning soil of organically derived fertilizer — Milorganite is my fertilizer option of choice. While chemical fertilizers can burn grass and quickly leach away, contributing to nutrient pollution in ponds, lakes, and bays, at least 80% of the nitrogen in Milorganite is water insoluble, meaning it will stay put and is slow-release, feeding the lawn for months.

Step 8: Mow Low Before Seeding

Turf grass should typically be cut no lower than 3½ inches to keep it healthy and looking great. But right before applying grass seed, set your mowing deck to 1½  to 2 inches to clear the deck. This will make it easier for the seed to penetrate the existing turf and reach the soil. It will also allow more light to reach the sprouting grass.

Step 9: Put Down Grass Seed

Now that the lawn is dethatched, aerated, amended, fertilized and cut low, it is primed for seeding. Use a broadcast spreader to overseed the whole lawn, not just the really bare spots. This will help the turf achieve the uniform appearance of a great-looking lawn.

Step 10: Attend to Trouble Spots

For those spots that are especially troublesome and bare, go over them with a cultivator to loosen up the soil surface for better contact with the seeds. Apply extra seeds by hand, and top dress with a sprinkling of compost or soil. You can even go the extra mile and add straw on top of everything to retain moisture and discourage foraging wildlife so the vulnerable grass seeds have an even greater chance to sprout and grow strong roots.

After week three, the new grass will be ready for its first mow. In a few weeks, your lawn will look as good as ever, if not better.