Zoysia grass is a popular warm-season turf, valued by homeowners across the southern United States and the transition zone for its dense, carpet-like appearance and durability. This grass thrives in heat and offers resistance to drought and heavy foot traffic. Homeowners often mix Zoysia with other grasses to address two issues: the temporary browning during winter dormancy and the grass’s slow rate of establishment after planting or damage. The goal of mixing is typically not to create a permanent blend but to use a temporary companion grass that addresses Zoysia’s weaknesses without competing during its active growing season.
Understanding Zoysia Grass Characteristics
Zoysia is classified as a warm-season grass, meaning its peak growth occurs when temperatures are consistently warm, generally between 80 and 95 degrees Fahrenheit. Like other warm-season varieties, Zoysia enters a state of dormancy when soil temperatures drop below 55 degrees. This causes the turf to turn a straw-brown color until spring warms the soil again. This winter discoloration is the primary motivation for temporary overseeding.
The grass spreads laterally through both above-ground runners (stolons) and below-ground stems (rhizomes), creating a thick, dense turf that naturally crowds out weeds. This aggressive lateral growth means Zoysia establishes slowly from seed and takes time to recover from damage or fill in bare spots. This slow establishment is the second reason homeowners sometimes look to mix in a faster-growing grass, at least temporarily, for quicker coverage. Zoysia maintains a low growth habit and requires less nitrogen fertilizer compared to other warm-season grasses.
Cool Season Partners for Winter Green Up
The most successful form of mixing with Zoysia is temporary winter overseeding with cool-season grasses to maintain green color during Zoysia’s dormant period. The ideal partner germinates quickly, provides deep green color through the winter, and naturally dies off when the Zoysia begins to green up in the spring. This temporary turf bridges the gap between autumn and spring, preventing the lawn from appearing brown.
Annual Ryegrass is frequently used for this purpose because it germinates very quickly, often within 7 to 10 days, and provides immediate winter color. Its annual nature means it is not meant to persist through the summer heat, reducing the risk of competition with the Zoysia when it exits dormancy. The intent is for the Ryegrass to succumb to the rising spring temperatures, allowing the Zoysia to take over seamlessly as it resumes active growth.
Perennial Ryegrass can also be used for overseeding, offering a finer texture and a darker green color than its annual counterpart. However, caution is necessary because Perennial Ryegrass is more persistent and may not die back quickly enough in the spring. If it persists too long, it can actively compete with the emerging Zoysia for water, light, and nutrients, potentially stressing the warm-season turf. Tall Fescue can also be used for winter overseeding, particularly on sports turf, due to its moderate competition in spring and visual similarity to Zoysia.
Grasses That Do Not Mix Well
Permanent mixing of Zoysia with other grass types is generally not recommended, especially with other warm-season species, because of their differing competitive natures and maintenance requirements. Zoysia is an aggressive spreader that forms a dense canopy and will often choke out less vigorous species. Attempting to mix Zoysia with another aggressive warm-season grass, such as Bermuda grass, typically results in an uneven, patchy lawn as one species dominates the other.
Bermuda grass is known for its aggressive growth rate and can often outcompete Zoysia for resources in full sun areas. Mixing Zoysia with cool-season grasses for a permanent blend, such as Tall Fescue or Kentucky Bluegrass, leads to an unattractive, non-uniform appearance. These cool-season grasses often grow in clumps or patches, creating a distinct color and texture difference that is visually jarring against Zoysia’s fine, dense turf. Furthermore, Zoysia and cool-season grasses require different mowing heights, fertilization schedules, and watering amounts during the summer, making a blended lawn difficult to maintain.
Mixing Techniques and Timing
For successful winter green-up, the timing of overseeding is the most important factor. It should occur in the late fall when the Zoysia is starting to go dormant, but before the first hard frost. The ideal window is when soil temperatures are consistently between 65 and 70 degrees Fahrenheit, which typically corresponds to nighttime air temperatures dropping below 65 degrees. This timing ensures the cool-season seed can germinate quickly while the Zoysia’s growth has slowed, reducing competition.
Preparing the existing Zoysia lawn involves mowing the grass shorter than usual, down to about 1 to 1.5 inches, to expose the soil. Because Zoysia produces a thick layer of thatch, dethatching or aerating the lawn before seeding can significantly improve seed-to-soil contact and germination rates. Once prepared, the ryegrass seed should be spread evenly across the lawn using a calibrated rotary spreader, often at a rate of 5 to 10 pounds per 1,000 square feet.
After seeding, the lawn must be kept consistently moist with light watering multiple times a day until the cool-season grass seedlings emerge, which usually takes about a week. Once the seedlings are established, the watering frequency can be reduced, but the depth of watering should increase to encourage deeper root growth. For repairing small bare spots during the warm season, the best approach is to use Zoysia plugs or seed, as the Zoysia will eventually fill itself in from its stolons and rhizomes.