Zoysia grass is a warm-season turf variety prized for its dense growth habit and tolerance for heat and drought. Dormancy is a natural survival mechanism that allows the grass to protect its core living structures, like the crown and root system, from cold injury and resource depletion during the winter months. This biological shutdown is a predictable part of the turf’s annual life cycle, ensuring it can return vigorously when favorable growing conditions resume.
Environmental Triggers That Initiate Zoysia Dormancy
The primary signal that causes Zoysia grass to enter dormancy is a sustained drop in temperature, specifically within the soil. Zoysia’s metabolic processes begin to slow significantly when the soil temperature consistently falls below 65°F, with the full onset of dormancy occurring when the 4-inch deep soil temperature drops to approximately 55°F or lower. This temperature threshold causes the plant to halt shoot growth and withdraw resources from its leaf blades, conserving energy in the underground structures.
Although soil temperature is the most reliable indicator, the calendar date is unreliable because the onset of dormancy varies significantly by region. In the northern parts of the transition zone, Zoysia may begin to turn color in late September or early October, while in the deep South, it may remain green well into November. The first hard frost often serves as a visual marker, causing the rapid browning of the leaf tissue and accelerating the shift to dormancy.
Decreasing daylight hours, known as photoperiodism, also plays a secondary role in preparing the turf for the winter rest period. The shortening days signal to the plant that winter is approaching, contributing to the physiological changes that precede temperature-driven dormancy. This combination of colder soil and shorter days ensures the grass is fully prepared to withstand winter conditions.
Visual Appearance During the Dormant Period
Once Zoysia grass enters its dormant state, the vibrant green color of the active growing season changes to a uniform straw or golden-brown hue. This color change is not an indication of death but rather the result of the plant withdrawing chlorophyll and nutrients from the leaf blades. The grass blades themselves will feel dry and look lifeless, but the vital crown remains alive and protected just above the soil line.
A simple “tug test” can help distinguish this normal dormancy from turf death or disease. Dormant grass blades will resist a gentle pull because the healthy root system is still anchored firmly in the soil. If the grass pulls out easily and the crown appears shriveled or crumbly, it is likely dead. This uniform brown appearance also differs from the irregular, circular patches of brown patch fungus, a common disease that creates distinct, expanding rings of discolored grass.
The dormant state differs from the gray-blue cast that Zoysia may take on during severe summer drought stress. Drought-induced dormancy is a temporary survival mechanism that can be quickly reversed with water. In contrast, cold-induced winter dormancy is a deep, biological rest that requires sustained warm temperatures to break, and the grass will maintain its uniform tan color throughout the winter.
The Return to Active Growth
The return of Zoysia grass to active growth in the spring is primarily dictated by a reversal of the winter’s low-temperature trigger. This process, often called “greening up,” begins when soil temperatures rise and stabilize consistently above 65°F at the 4-inch depth. This sustained warmth signals to the plant’s crown and root system that the threat of cold has passed, prompting the re-allocation of stored carbohydrates for new shoot growth.
Because the calendar date is unreliable, the precise timing of green-up varies widely, sometimes occurring as early as late March in the southern transition zone or as late as mid-May farther north. The process is gradual, and the grass will often appear mottled or patchy as different areas of the lawn respond to microclimate variations in soil warmth. Zoysia is typically one of the last warm-season grasses to fully green up in the spring.
Cool-season grasses, like fescue, which may be present in the lawn, will begin their active growth much earlier, sometimes creating green patches within the dormant Zoysia. The slow, temperature-dependent emergence means Zoysia requires patience, but once the soil reaches optimal temperatures, the grass will rapidly transition back to its dense, vibrant green state.