Overseeding Zoysia Grass: How-To Guide with Easy Steps

Zoysia grass is a warm-season turf from Asia which thrives in central and southern states. It grows thick, which can make it ideal for lawns and golf courses. However, even with the best care, drought, pest damage, and cold weather can cause zoysia to turn brown and go dormant. If there’s extensive damage, bare spots can form. Overseeing zoysia can help restore the turf. This how-to guide walks homeowners through the easy steps needed to overseed zoysia grass.

What is Zoysia?

Zoysiagrass, or zoysia, is a warm-season grass that’s native to Japan, China, and other parts of Southeast Asia. With a dense, carpet-like texture, it’s a common choice for lawns, golf courses, and sport fields, especially in warmer climates. It’s popular across the south and central portions of the United States.

Zoysia has several benefits over other types of grasses:

• Durable: Zoysia’s grass blade density means the grass can stand up to heavy use and foot traffic.
• Heat-tolerant: Zoysia thrives in hot climates. In cold weather, the grass goes dormant and turns brown. When the higher temperatures return, zoysia will turn green again.
• Drought-tolerant: This turfgrass requires much less water compared to other types.
• Low-maintenance: Zoysia is slow-growing and requires little mowing, fertilization, or landscaping. In addition, thanks to its density, the grass often doesn’t need herbicide.
• Improved weed control: Its density helps prevent weeds from growing.
• Shade-tolerant: This type of grass prefers the full sun, but it can still grow and thrive in light shade.

Should You Overseed Zoysia?

In most cases, zoysia doesn’t require overseeding. The grass grows so thick that overseeding may not be possible. Even seeds that managed to reach the soil would have a hard time growing due to the carpeting effect of zoysia. The sun simply couldn’t reach the sprouting grass.

However, though zoysia is durable and can withstand heavy foot traffic better than other types of grass, bald spots can still develop. While you could wait for the grass to return on its own, overseeding zoysia can thicken the lawn in a fraction of the time. Overseeding months in advance can also result in a fuller lawn during the spring and summer.

In areas that see both hot and cold weather, zoysia can go dormant and turn brown during cold weather. Although it returns to its active state with warmer temperatures, this can result in an unattractive lawn during the colder months. To help the yard stay a lush green, some homeowners opt to overseed the existing lawn with cool-season grasses, such as perennial ryegrass, during this time.

What Makes Zoysia Grass Patchy?

Before overseeding zoysia grass, you’ll need to identify the root cause of the damage or the problem will return. Zoysia is resilient, but it isn’t invincible.

Common causes of patchiness in zoysia include:

• Chinch bugs, the most common pests of zoysia, are active during the summer months and their impact can resemble drought effects. However, chinch bugs begin damaging grass from one side and expand as populations increase. Damage will be most severe along lawn boundaries, such as sidewalks and driveways.
• Hunting billbugs are active during the night and early morning. Billbug larvae bore into the zoysia’s lower leaf stem during mid-spring to early summer, which can result in extensive damage. The grass will turn from green to yellow to brown before dying.
• Rhizoctonia solani is a soil-borne fungal pathogen. Large patches, ranging from 6 inches to several feet in diameter, will appear in the fall and worsen as zoysia growth slows due to cooler temperatures. 
• Overwatering, standing water, and poor drainage can cause root rot, make the grass more susceptible to disease, and attract grubs. 
• Extreme heat and drought stress grass. Although zoysia is drought- and heat-resistant, little water and extreme high temperatures can cause the grass to die.
• Thatch is a layer of dead and living grass stems, roots, and organic material on the soil surface. If the thatch is thick, it can prevent water, air, and nutrients from reaching the zoysia. It’s more common in over-fertilized lawns.

Other causes of brown zoysia and patchiness include excessive shade, imbalanced soil pH levels, improper mowing, poor seeding practices, competition with trees and other plants, moles, and grubs. If the patchiness is due to insects or disease, you’ll have to target the root cause before you start overseeding.

How to Overseed Zoysia Grass — 8 Easy Steps

If you need to overseed your zoysia, it’s a simple DIY project. Follow these eight steps. 

1. Choose the right time of year. You should overseed zoysia in the late spring or early fall as temperatures are favorable for seed germination. If you overseed in the fall, spread seeds at least 60 days before the first frost.
2. Collect debris. To prepare the seedbed, remove debris, including stones, rocks, pinecones, straws or any other ground cover. Use a rake to collect and remove smaller pieces. If you’re seeding a bare spot, remove any dead grass to expose the soil.
3. Mow. Cut the grass to about 1-inch tall for better seed-to-soil contact. When grass is high, seeds get stuck in the blades and may not reach the soil. 
4. Aerate the lawn. Punch holes into the ground to loosen compacted soil. This allows the water to penetrate deeper and better reach root systems. Aerated soils also improve seed-to-soil contact.
5. Dethach. Remove any dead grass or organic material you find to prepare the existing turf. Dethaching allows more water, air, and nutrients to reach the grass.
6. Check the soil and fertilize. Check the soil for nutrient deficiencies and apply a fertilizer based on the soil test’s recommendations. Zoysia needs more nitrogen, little to no phosphorus, and less potassium.
7. Buy the right amount of seeds. Zoysia needs two pounds of seed per 1,000 square feet. You can calculate the amount of grass seed needed by dividing your lawn area by the recommended seeding rate. 
8. Plant grass seed. A hand spreader or push spreader is ideal for spreading zoysia seeds evenly.

Under ideal conditions, you’ll start to see growth in 14 to 21 days.

Maintaining an Overseeded Lawn

To keep your zoysia lawn lush, the grass needs proper maintenance. Here are some tips:

• Water the lawn. Overseeded zoysia lawns need good moisture to sprout seed. Initially, water daily until germination. The recommended rate is 1 inch of water per week, including rainfall.
• Don’t overwater. Overwatering attracts pests and can cause root rot. Take regular measurements of water for a healthy lawn.
• Add fertilizer as needed. The best time to fertilize zoysia is during its growing season in late spring or early summer. It helps the lawn thrive and reduces the risk of insect damage. Always do a soil test before adding fertilizer.
• Mow to the correct height. Zoysia should be kept to a height between 1.5 inches to 3 inches for the best health. Keep in mind that zoysia will require less mowing compared to other types of grass.

Final Thoughts About Overseeding Zoysia

Zoysia is a popular choice for homeowners and golf courses that are looking for a durable grass that can stand up to heavy traffic, high temperatures, and droughts. This type of grass doesn’t usually require overseeding, but pests, extreme weather, and poor lawn care practices can result in brown or dead patches. Following these simple steps can help your zoysia lawn thrive.