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Finding a turf grass that grows well in clay soil can be challenging, and maintaining it can be even harder. Homeowners are constantly looking for a turf grass that will handle difficult soil without too much hassle.
One of the most popular choices for poor soils is zoysia. It grows laterally and quickly fills in bare spots without getting too tall. You can get away with mowing every couple of weeks and a light irrigation schedule, and it thrives throughout the southern half of the United States.
But will zoysia grass grow in clay soil? Yes, zoysia will grow in clay soil. However, zoysia doesn’t handle wet growing conditions, so focus on aerating each spring and practicing consistent thatch maintenance. Good drainage is the key to growing zoysia in clay.
Clay is a mixture of the best and worst qualities a soil can have. While it holds on to valuable nutrients better than any other soil texture, it lets in almost no oxygen, which leads to a host of problems.
Let’s make sure you understand the challenges and requirements that you’ll need to keep in mind.
Understand The Challenges Of Clay Soil
Clay soil has one fundamental flaw that makes it the most difficult soil to improve: low porosity.
Ideally, soil should be 50% matter and 50% pore space (source). These pores should be varied in size to allow both oxygen and water to enter and exit the soil freely.
Low porosity means there are fewer pore spaces, and the available pore spaces are small. This results in water that is either unable to permeate the soil (in dry climates), or water that is unable to drain from the soil (in wet climates.).
Low porosity also makes it difficult to incorporate organic matter, like compost, into the topsoil. Earthworms have a difficult time moving through the soil and pulling down dead leaves, and water can’t wash organic materials down into larger pore spaces, because they don’t exist.
This can result in a compost topdressing sitting on top of a layer of clay and forming a thick, organic sheet that is separate from the topsoil. When this happens, grass grows in the organic layer, but the roots cannot penetrate into the clay below, which results in a very shallow root system that easily succumbs to pest, disease, and drought.
Maintaining Zoysia in Clay Soil
If you already have an established zoysia lawn, there are a few steps you can take to improve clay soil without too much disruption to the roots:
- Dethatch as necessary
- Core aeration
- Topdressing with compost
Dethatch as Necessary
Most lawns grown in clay soils build up an unhealthy amount of thatch. Dead leaves, roots, and grass clippings take a long time to decompose and incorporate into the tight pore spaces between clay particles, so thatch tends to build up quickly.
Zoysia can handle an aggressive dethatching or power raking. Zoysia grows laterally by sending out above-ground stolons and below-ground rhizomes to sprout up new bunches of grass. Dethatching cuts through the stolons and pulls up the thatch layer, but it leaves the rhizomes intact, meaning the lawn can recover quickly.
Dethatch in late spring or early summer right after the lawn begins actively growing. This ensures the lawn will fill in quickly and is not at risk of going dormant due to drought.
If your lawn has less than ½” of thatch, it is actually beneficial. Thin thatch layers help prevent evaporation and add organic matter into the soil. If you decide you need to remove built-up thatch, do this step before aeration.
However, you may not need to dethatch at all if you are consistently aerating and topdressing each spring.
The most important aspect of improving clay soil is integrating organic matter into the clay to improve porosity. This is easy to do in the spring and fall by aerating and then raking in a layer of compost.
There are two ways to aerate a lawn: core aeration and spike aeration. Core aeration pulls out cores of soil, leaving holes which can then be filled by a layer of compost. Spike aeration pushes spikes deep into the soil to allow oxygen to penetrate. This is a great method for some lawns, but the holes made by spikes are too small to be filled by compost.
Aerate in early summer, after the grass is actively growing, and after dethatching (if necessary). You can also aerate again in the fall, but no later than a month before the first frost.
Mow your lawn a few days before you plan to aerate, and then water thoroughly. This will allow the aerator to penetrate the soil easily, and it will allow you to pull out deeper cores.
You can be aggressive when you aerate zoysia because it fills in so easily, although patches that are in the shade or low spots that hold moisture may take longer to fill in.
Aerators will allow you to adjust the depth of the core, the spacing of the holes, and the diameter of the holes. Set your machine to the widest diameter, deepest depth, and closest spacing so that you can add the maximum amount of compost back into the soil.
Topdressing with Compost
After you aerate, spread a layer of compost over your lawn and rake it into the holes. This will incorporate organic matter directly into the root zone, and as the roots take hold in the compost, it will gradually mix in to the clay surrounding it.
Most lawns will be too large to buy compost by the bag for topdressing. To apply a ½” thickness of compost over 100sq’, you would need approximately 7 bags. This adds up quickly, which is why it is better to buy in bulk from a garden supply center. In order to do this, you need to calculate the number of cubic yards it will take to cover your lawn.
- First, calculate the square footage (length x width).
- Next, multiply the square footage by .5” (you may need more after aggressive aeration).
- Finally, multiply this number by .0031, which will give you the number of cubic yards.
For example, if your lawn is 30’x50’, you would do the following:
30 x 50 = 1500 square feet
1500 x .5 = 750 cubic feet
750 x .0031 = 2.325 cubic yards
Most garden centers work with whole yards, meaning you will need to round up to the next whole number. If you have extra compost, spread it thicker underneath established trees and landscapes.
After topdressing, spray or spread a pre-emergent herbicide to keep weeds from sprouting in the fresh compost.
Clay has a high nutrient-holding capacity, and zoysia has low nutrient requirements. If you topdress each spring, you shouldn’t need to add any additional fertilizers unless your soil tests show a deficiency.
Note: Clay can also hold onto pesticides and insecticides. Click here to learn more.
Establishing Zoysia in Clay Soil
If you’re starting from scratch, you have more options for improving difficult clay soil before installing a new lawn.
Zoysia is one of the best lawn choices for clay soil in warm climates, which means you can focus on improving the soil you have instead of replacing it.
First, do a soil test. They are relatively inexpensive online (link to Amazon). Zoysia tolerates a pH of 5.8-7.0, which is good news for homeowners with a high clay percentage, because clay tends to be more acidic than other soil types but this can vary depending on region. A soil test will provide definitive answers specific to your area.
If your soil’s pH is too low, use limestone to bring it up (source). Clay can take a while to respond to amendments, so you may have to reapply lime each year. It is difficult to modify the pH of clay soils, but luckily, zoysia tolerates a wide range and handles acidic soils better than most other turf grasses.
Zoysia is a light feeder, which means it can thrive in average soils. Instead of adding amendments or fertilizers, bring in compost and till it into the top 6” of your soil. Compost will introduce a source of slow-release nitrogen and small amounts of other nutrients which should provide adequate nutrition for a new lawn.
The only true risk of growing zoysia in clay is wet feet, or a soil that drains slowly and keeps the roots saturated. This is much easier to combat when you’re working with a blank slate. Adding in large amounts of compost will help increase porosity in your soil, which will improve drainage and keep your lawn healthy.
To calculate the amount of compost you need, use the same formula for calculating a topdressing, except use a depth of 3”-6” depending on the amount of clay in your soil. The higher percentage of clay you have, the more compost you need.
So, if your lawn is 30’ x 50’, and you want a 3” layer of compost, you will calculate:
(30 * 50) (3) (.0031) = 13.95 cubic yards
Spread the compost over the lawn area, and till it in on the deepest possible setting. Try to avoid as much foot traffic as possible to prevent compaction. Till when the soil is moist, not wet, and till only as much as absolutely necessary. Over-tilling leads to compaction.
Sod, Plugs, Sprigs & Seed
The most common way to install zoysia is with live turf. Once zoysia has a firm root system, it can fill in quickly. However, this can take up to two years depending on the installation method.
Sod gives you an instant green lawn, and it also keeps weeds from sprouting and taking over. Sod is rolled out over your prepared soil, so any dormant weed seeds will get buried, meaning you’re way ahead of the game as far as weed management. Sod is the best choice for clay soils because it is the easiest to keep moist.
Plugs are the second-fastest installation method, but they are much slower than sod. Space plugs 6”-12” apart and keep moist. Once the plugs take root, they will quickly spread and fill in the bare spots.
However, this could take one full growing season. This means frequent weed management in the first few years to ensure a lush, tidy stand of grass. Be sure to purchase from a reputable grower where they are guaranteed to grow or replaced free (link to Zoysia Farms).
Sprigs are shredded pieces of sod. It is considerably cheaper to use sprigs rather than sod, but it is much more labor-intensive. Sprigs must be spread over the soil, rolled or tilled in to the soil, covered with straw (optional) and kept moist for the first 3-6 weeks after planting.
You must be willing to allow the weeds to grow with the grass, because weed treatment too early will harm the grass. Once you’ve mowed a few times, you can begin fighting back the weeds. Using a high-quality compost and going through the soil-prep guidelines for a lawn will cut down on weed growth considerably.
Seeds are the most cost-effective option for establishing a zoysia lawn, but they can be difficult to find. While it’s not always in stock, Amazon carries zoysia seed (click to check pricing and availability).
Besides being economical, the biggest advantage to seed is coverage.
While zoysia has a slow germination rate (some seed can take up to a year to take root), you can spread seed more dense than sprigs and plugs, which can help choke out weeds once the grass takes root.
Use straw (not hay) to spread over seeds and help retain moisture. Straw will break down and add organic matter into the clay, which will help with porosity over time.
Once you’ve established a stand of zoysia, continue to aerate and topdress each growing season. This will continue to add organic matter into the soil, which will improve porosity and prevent compaction.
Irrigate an established lawn with 1 inch of water each week. Follow a deep and infrequent irrigation schedule so that roots continue to grow down into the clay searching for moisture.
Choosing Zoysia Installation Options
|Sod||Instant lawn, less weeds from the start||Expensive|
|Plugs||Less expensive for larger areas||Requires weed control|
|Sprigs||Even less expensive||Labor intensive, requires weed control, longer time to fill in|
|Seeds||Most cost effective for very large areas||Difficult to find, longest process to a complete lawn.|
Zoysia can be an expensive lawn to establish, but it may also be the most long-term cost-effective choice for clay soils in warm climates. Zoysia is incredibly low maintenance, and it handles the pitfalls of clay soil better than most other warm-season turf grasses.
Recommended Reading: Improve Clay Soil for New Or Existing Lawns