Zoysia grass is a warm-season turf known for its density, fine texture, and drought tolerance. During the growing season, it forms a lush, carpet-like lawn. As a warm-season grass, Zoysia enters a period of dormancy when temperatures cool, turning a straw-tan color. Homeowners often become concerned in the spring when the lawn fails to quickly revert to its signature green. This slow green-up is typically a result of environmental factors or underlying issues preventing the grass from reviving its growth cycle.
Dormancy and Soil Temperature
The single most frequent reason Zoysia grass remains brown in the spring is that the soil has not yet achieved the necessary sustained temperature. As a warm-season variety, Zoysia takes its cues from the ground, not the air, to break dormancy. It requires the soil temperature at a four-inch depth to consistently remain between 60°F and 65°F for several days before it initiates the transition back to green growth.
Despite warm daytime air temperatures, the soil can take significantly longer to heat up, especially if the area has experienced a wet or cloudy spring. Early warm spells may temporarily encourage a slight color change, but a subsequent cool snap or a prolonged period of cool nights will halt the green-up process. This delay is normal and protects the grass from late-season frost damage. The uneven greening often seen near sidewalks or driveways occurs because these hard surfaces absorb and radiate heat, warming the adjacent soil faster than the rest of the lawn.
Nutritional Deficiencies
Once soil temperatures are adequate, a lack of deep green color often points to a nutritional imbalance hindering chlorophyll production. Nitrogen (N) is the primary nutrient responsible for vibrant green color and vigorous leaf growth. If the lawn was under-fertilized the previous year or the early-season application was insufficient, the grass lacks the necessary building blocks to rapidly green up.
A deficiency in the micronutrient Iron (Fe) is also common and is essential for chlorophyll synthesis. Iron deficiency is particularly common in Zoysia lawns where the soil pH is alkaline (higher than 7.0). In these high-pH conditions, Iron becomes chemically unavailable to the grass roots, resulting in chlorosis, or a yellowing of the new, younger leaf blades. Applying a foliar Iron treatment can often provide a rapid, temporary color boost without promoting the excessive top growth that high nitrogen applications would cause.
Water Management and Soil Health
Even with adequate temperature and nutrient levels, physical soil constraints can inhibit the root system’s ability to absorb what is needed for spring growth. Heavy foot traffic or the natural settling of clay-heavy soils can lead to soil compaction, reducing the pore space needed for air and water movement. This lack of oxygen around the roots slows metabolic activity and prevents the grass from transitioning out of dormancy efficiently.
In addition to compaction, moisture extremes during the transition period can also cause the grass to remain brown. Too much water, often from poor drainage or excessive spring rain, can lead to waterlogged soil, which suffocates the roots and promotes fungal diseases. Conversely, if the grass is allowed to dry out too much, it may enter a drought-induced dormancy, which keeps it in a brown state even if temperatures are high. Deep, infrequent irrigation encourages a robust root system capable of supporting a healthy green canopy.
Pests and Disease Damage
In some cases, the failure to green up is not a simple delay but a symptom of biological damage that occurred during the cooler months. The most damaging fungal issue for Zoysia is Large Patch, caused by the pathogen Rhizoctonia solani. This disease typically manifests in the spring as the grass attempts to break dormancy, causing large, circular or irregular patches of turf to turn tan or brown. The patches fail to green up because the fungus attacks the grass at the base of the leaf sheaths and stolons.
Subsurface pests, such as white grubs or billbug larvae, can also cause localized areas to remain brown by feeding directly on the root system. Grubs consume the roots, making it impossible for the grass to take up water and nutrients necessary for spring revival. A sign of this damage is the ability to easily pull up sections of the turf, like lifting a piece of carpet, because the roots have been severed.