How To Avoid Killing Grass After Dethatching Your Lawn

Thin, patchy spots in your lawn are never a good sign, but they can pop up, even when you're taking proper care of your lawn. In some cases, dry or spongy patches indicate that your lawn needs dethatching. When the thatch layer that collects on your soil gets too thick, it prevents water and nutrients from penetrating the soil and blocks air from reaching the lawn's roots, which affects the health of the grass. A thick thatch layer also makes your grass more susceptible to diseases. Fortunately, dethatching can help restore your lawn to its full health, but there's a catch: it can leave the grass in a stressed state in the immediate aftermath. To prevent killing your grass after dethatching, it's essential to take proper care of it by removing the debris, aerating, watering, fertilizing, and overseeding your lawn.

Thatch is a layer of dead plant material that builds up on your lawn's soil — a thin layer is normal in health lawns. When it's only ½ to ¾ inch thick, it's not a problem and can actually keep the soil moist and prevent compaction. However, when it is more than ¾ inch thick, it's time to remove it. Dethatching a lawn involves removing the thatch layer using an electric dethatcher, a manual dethatcher, or another tool to cut through the material. While it benefits your lawn's health in the long run, removing the debris leaves the grass vulnerable and exposed temporarily. You can keep your lawn from dying, though, just by giving it a little TLC.

If you've avoided most of the crucial mistakes that everyone makes when dethatching, your lawn should be in decent shape. However, it will still likely be stressed and require some help in getting the necessary nutrients for recovery. After dethatching, your lawn will be covered with bits of dead grass and other organic material. If this material remains on top of the lawn, it blocks air and sunlight from reaching the soil and grass roots. Rake up the remaining pieces of thatch scattered across your lawn, and gather them in a trash bag for disposal or toss them in your compost pile.

After dethatching, it's also a good idea to aerate your lawn. Aerating is the process of removing cores of soil to help reduce compaction and provide pathways for water, nutrients, and air to reach the grass roots. A plug aerator is the best tool for the job, so look for a model that can make holes in your lawn approximately 2 to 3 inches apart with a diameter of ½ to ¾ inches.

Removing the thick thatch layer usually exposes the grass roots, which can cause them to dry out. That's why watering your lawn should be your next step. Not only does it help to protect the roots, but it can also settle any soil that's been disrupted by the dethatching. Give it approximately 1 inch of water, so the soil is fully moistened without being waterlogged.

After a thorough dethatching, your lawn usually needs a boost of nutrients to help it recover. Applying a high-quality fertilizer can help your grass continue to grow. Deciding which fertilizer is best for your lawn can be tricky, but consider your grass type and the season. Cool-season grasses do well with fertilizers with higher phosphorus, so look for a formula with an NPK ratio of 18-24-12 to ensure healthy root growth. Warm-weather grass needs a balanced formula with a 16-16-16 NPK ratio. Follow the rate recommendations on the fertilizer packaging, and use a broadcast spreader for even application.

Next, you should fill in any bare spots or thin patches after dethatching. It is the perfect time for overseeding because the seeds will have plenty of contact with the soil with the thatch removed. Choose grass seeds that are compatible with the region you live in and your existing grass type.  Loosen the soil in the areas you plan to seed, spread them evenly, and then rake them in for better seed-to-soil contact.

Once you've fertilized and seeded your lawn, adding a layer of top dressing to the grass can help protect it during its recovery. Apply a ¼-inch layer of compost or topsoil over the lawn, and spread it evenly across the grass with a rake.