Zoysia grass is a warm-season turfgrass known for its dense, carpet-like growth during the summer months. Like other grasses adapted to hot climates, Zoysia enters dormancy when soil temperatures drop in cooler seasons. This protective mechanism causes the grass to lose its green pigment and take on a straw-brown color. This change is a normal part of the plant’s annual cycle, and the grass will transition back to a vibrant green when conditions become favorable.
Required Soil Temperatures for Green-Up
The trigger for Zoysia grass to emerge from dormancy is the sustained temperature of the soil, not the air temperature. Since biological processes occur in the root zone, soil temperature is the most important factor. Initial waking, where the first sporadic green shoots appear, begins when the soil temperature at a two- to four-inch depth consistently reaches 55 degrees Fahrenheit for several days.
Full green-up and active growth require a warmer environment, usually when the soil remains at or above 65 degrees Fahrenheit. This higher temperature range supports the metabolic activity needed for the grass to produce new leaves and rhizomes. The process is gradual, often starting as small, bright green patches in the warmest areas of the lawn before spreading across the full turf.
Homeowners can monitor this measurement using a simple soil thermometer inserted four inches into the ground, taking a daily reading in the mid-morning. Public resources, such as university extension websites, often provide daily soil temperature averages for local zip codes, which serve as a reliable guide. Waiting for these specific temperature thresholds ensures the turf is physiologically ready to begin its growing season.
Variables That Affect Dormancy Timing
The time it takes to reach the required soil temperature threshold can vary significantly, even between nearby properties. Geographic region is a major determinant, particularly for lawns in the Transition Zone, where cold winters and hot summers meet. In this zone, spring warm-up is often inconsistent, leading to slower and more unpredictable green-up compared to the Deep South.
Microclimates within a single lawn also play a role in the timing of the transition. Areas receiving full, unobstructed sunlight absorb solar energy more efficiently, causing the soil to warm faster. Conversely, sections heavily shaded by trees or buildings retain cold soil longer, delaying the start of green-up by days or even weeks.
Differences between Zoysia cultivars influence the speed of emergence from dormancy. While Zoysia is known for its cold tolerance compared to other warm-season grasses, specific varieties have been bred for different characteristics. These variations may include differences in how quickly they respond to rising soil temperatures.
Spring Lawn Care During the Transition
The period just before and immediately following green-up is a sensitive time for the lawn, requiring specific care actions. One important task is the timely application of a pre-emergent herbicide, which should be done before soil temperatures reach 55 degrees Fahrenheit. This application creates a chemical barrier that prevents the germination of warm-season weeds like crabgrass, which begin to sprout at this lower temperature.
When the grass begins to show active growth, an initial, low mowing pass should be performed to remove the dead, dormant leaf tissue. This process, often called scalping, should be done with a sharp blade at a height lower than the regular season cut, without damaging the crown of the plant. After this initial cut, the mower height should be raised to the turf’s regular maintenance level.
The first application of nitrogen fertilizer must be carefully timed to avoid feeding emerging weeds and stimulating excessive leaf growth before the root system is fully active. Wait until the Zoysia turf is at least 50 percent green before applying a slow-release nitrogen product. Fertilizing too early directs energy to the top growth at the expense of root development, which can weaken the turf and increase its susceptibility to diseases like large patch.