How To Grow Grass In Clay Soil And Grow A Beautiful Lawn

Clay soil is made up of tiny mineral particles with very little organic material to separate all those microscopic rocks. And it's usually very alkaline. How can you grow grass in it when the roots have to struggle to find nutrients that are locked up by alkalinity?

I have battled clay soil and turned it into my friend. You can do the same. Let me show you how to grow grass in clay soil and grow a beautiful lawn.

It is possible, but there is some hard work and expense involved. In a nutshell, you have to correct your soil's pH, add organic material and overseed.

You can succeed with clay soil whether you're planting a new lawn or rehabilitating a long-existing one. Each lawn has variables, like bare spots or very high alkalinity, that need to be addressed. I'll explain how to go about each task outlined below in a way that best suits your own particular situation.


Skip this step if you don't have thatch. If you do, you need to get rid of as much of it as possible. If you're tearing your lawn up and creating a new one, this is easy. The thatch that doesn't get removed along with the living grass will serve as extra organic material.

To dethatch a lawn you're going to keep, go over your working area twice with a good thatch rake or powered dethatcher. Rake up the thatch, and add it to your compost pile or the organic matter you'll use to amend your clay. Now would be a good time to dethatch your entire lawn, not just the parts you are working.

Fix Your Ph

You need to know how high your soil's alkalinity is before you can adjust it. You can get a simple soil tester for about $10. Vivosun makes an accurate, low-priced meter that tests pH, moisture and sunlight levels. You just stick it in the ground in several spots throughout your lawn and average the pH readings.

The optimal pH for a lawn's soil is 6.5. Anything lower than that is acidic.

Higher numbers are alkaline. If your soil is alkaline, and it almost certainly is, you'll need to spread some granulated sulfur. Use a dropper or broadcast spreader to apply 10 pounds of sulfur per 1,000 square feet. This will bring your soil down one-half of a point. If you need to drop your alkalinity by an entire point, like from 7.5 to 6.5, apply twice as much. Any more than a one-point drop should be done in two applications spaced three months apart.

After you spread your sulfur, wait eight weeks and check your pH again. If this means you'll have to wait until tbe following year to actually plant seed, so be it. With this project, it's best to get each step done right before moving on to the next. Once you get your pH right, the grass roots will be able to use the nutrients in the soil.

Add Organic Material

Now we need to make the soil looser so roots can grow into it. Some people use sand or gypsum to break clay soil up. I highly recommend using organic matter instead. For one thing, it supplies nutrients that your beautiful new lawn is going to need. Another thing is that it's much easier to get the right ratio of organics to clay. It's almost impossible to overdo it. The ratio of inorganic material to clay, however, has to be pretty precise. If you add too much, you get inconsistent, loose soil. Add too little, and you literally end up with brick.

Compost, topsoil and manure all make fantastic amendments for clay soil. Don't use fill dirt. That's what you have now. Don't use wood chips either. They don't break up the soil enough, and a compound in decomposing wood locks nitrogen in the soil. You need enough material to add a level one-quarter to one inch on top of your clay. More is better. Just spread it on top. Your good grass will grow up through it, and your weak grass will die and become compost. You'll plant seed later to make your lawn thick and green.

If you are rehabilitating an entire lawn, or a big chunk of one, you would be better off working the amendment in with a tiller. You can use a plug aerator for smaller areas. Spread your organic material evenly over the area you're working, then till or aerate. If you have time, break this task up into two. Spread half of your organics, work it in and repeat the process. This will get your two soil types mixed up better.


First, determine what type or grass your lawn is made of. Ask your agricultural extension office for help, if you need it. You don't want to mix two types of grass, but you want to make sure your lawn is tolerant of clay soil. You're improving your soil, but it's still clay. Here is a list of grasses that grow well in clay:

  • Tall rescue
  • Bermuda
  • Buffalograss
  • Zoysia

If your lawn currently consists of one of these, get the same kind of seed. If not, you may want to consider removing your existing grass and starting over with one of the above. That is a lot of work. You can still plant the same type of seed as your current lawn, but it may take a few seasons to get established well. If you have to make this choice, remember that it's better to have a lawn of uniform variety.

Broadcast your seed at the rate recommended on the bag. This will vary depending on the type of grass, whether you are planting a new lawn or overseeding.

Scatter some straw over the entire area you are planting. You can skip this step if you are overseeding, just be sure to work the seed down to soil level with a leaf rake. Either way, newly planted seed needs a good watering right away. Soak that good layer of mixed clay and organic matter well.

Water at least once daily, preferably around dawn, for the first week. If you've seeded in the beginning or middle of fall, which is the recommended time for most grasses, you'll see some slow growth throughout the cooler autumn and winter months. The fast, thick growth you're looking forward to will begin by the middle of the following spring. If you seeded in spring or summer, you should see quick growth within two or three weeks.

Keep everyone and everything off of your newly renovated lawn for at least a month.

This includes you and your mower!

Don't mow until your new grass is a good three inches tall. When you do mow, let your clippings fall where they may. Clippings don't cause thatch, but they do supply a continuing and free source of organic material for your new lawn. You just spent a lot of time adding biomaterial to your soil, so don't start depriving it now. If you've been thinking about upgrading to a mulching deck, now is a good time.

The First Year

Make sure your lawn gets at least an inch of water every week. If it doesn't rain enough, you'll have to water. This will ensure that the top six inches of soil gets some moisture.

Be sure to keep your mower blades sharp. As your lawn fills in, there will be many tender young grass shoots trying to fill in any bare spots. You want to slice them cleanly with the blade.

It would be a good idea to topdress once during the first year. Do this between late spring and late summer. The grass has to be actively growing. What happens is the grass will grow roots into the new organic material that works its way to the top of the soil. That's why topdressing is such a great way to continue adding organics to your lawn. It swallows it up.

Year Two And Beyond

Continue to provide at least an inch of water per week.

Keep an eye on your pH. Yearly testing is fine. If anything, your soil may return to a more alkaline state, but it won't get as bad as it was when you started. Another dose of granulated sulfur will being the pH back to where it needs to be.

Aerate in the second year and every two to three years after that. Keep in mind that the best time to topdress with organic matter is right after aeration.

Topdressing should give your lawn all of the extra nutrients it needs. Dont use chemical fertilizers unless you see a serious deficiency of some nutrient. There is still some clay under your good top soil. The fertilizer can concentrate at the level where the clay meets the new soil. This can cause root burn.

You shouldn't notice any thatch for at least a few years. When you do, take care of it. Rake it up, though. It is organic, of course, but it's too thick to leave laying on your lawn. It takes too long to biodegrade above ground.

As the years go on, your good layer of rich topsoil will get thicker and thicker. The grass' roots will work to break up and loosen the clay soil below. Once you're sure that your soil is good and healthy, consider adding some earthworms to help keep your topsoil nice and loose. Uncle Jim's Worm Farm sells 1,000 red wigglers for about $30, to give you an idea about price. Spread worms in even handfuls throughout your lawn. They will soon establish a self-sustaining population.

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Ed Kirkland

Hi, I'm Ed, and I've been doing lawn work since my mid teen years, picking up jobs here and there mowing and helping with basic landscaping projects. I worked at a couple different lawn care / landscaping companies throughout my college years, and now thanks to the internet I'm able to make a share my knowledge and advice with people about lawn care and landscaping.