St. Augustine grass, a popular turf choice across the warm Southeast U.S. and Gulf Coast regions, requires a significant shift in care practices when winter arrives. This warm-season grass thrives in heat and humidity, but its needs change dramatically as temperatures drop. Understanding the different water requirements during the cooler months is necessary for maintaining a healthy lawn. Ignoring these seasonal changes can lead to fungal diseases or drought stress, compromising the turf’s resilience when spring growth returns.
The Winter State of St. Augustine Grass
As air temperatures consistently decrease, St. Augustine grass enters a state of slowed growth, manifesting as either semi-dormancy or true dormancy. In mild climates, such as parts of Florida and South Texas, the grass often remains green but slows its metabolic rate significantly to conserve energy. In cooler zones, like northern Texas and Louisiana, the grass enters true dormancy, causing the leaf blades to turn brown or tan. This browning is a natural survival mechanism, not an indication that the turf has died.
During this period, the grass’s root activity decreases, and the rate of evapotranspiration is significantly lower than in the summer months. Evapotranspiration is the process of water loss through evaporation and plant transpiration. Because the grass is not actively growing or losing much water, its need for supplemental moisture is substantially reduced. This slowed state typically occurs once the soil temperature consistently drops below 68°F, though growth slows when air temperatures fall below 55°F.
Factors Determining Watering Frequency
There is no fixed schedule for watering St. Augustine grass in the winter; frequency is determined by local environmental factors. The primary indicator for reducing water is the temperature threshold, meaning watering frequency should drop sharply once average daily temperatures are below 60°F. When the grass is fully dormant, it requires minimal to no supplemental water, often receiving enough moisture solely from natural rainfall.
Natural precipitation must be monitored closely, and supplemental irrigation should only be used to make up for a deficit in rainfall. If the area receives less than 0.5 inches of rain over a three-to-four-week period, supplemental watering is necessary to prevent dehydration. Tracking local weather helps prevent overwatering, which is a common mistake during the cooler season.
The frequency of watering is also influenced by the soil composition beneath the turf. Sandy soils drain moisture quickly and may require slightly more frequent, yet light, applications of water. Conversely, heavy clay soils retain water for longer periods, requiring much less frequent watering to maintain adequate root crown hydration. For mild winter zones, if temperatures remain consistently above freezing and there has been no rain, supplemental watering may be needed approximately every three to four weeks.
Essential Winter Watering Techniques
When supplemental watering is necessary, the method of application is as important as the frequency to ensure turf health. The goal is to provide light moisture primarily to the root crown and upper soil layer, not deep saturation of the entire root zone. Applying approximately 1/2 inch of water per irrigation event is sufficient to rehydrate the plant tissues without soaking the soil.
Applying too much water risks waterlogging the soil, which limits oxygen availability to the roots and creates conditions favorable for fungal growth. The timing of the watering session is also important to mitigate the risk of disease. Watering should be done in the late morning or early afternoon, ideally between 10 a.m. and 2 p.m. This timing allows the grass blades and the soil surface to dry completely before evening, minimizing the leaf wetness period that fungal pathogens require to thrive.
Before initiating watering, the top inch of soil should be checked for dryness to confirm the need for moisture. If the soil feels dry to the touch, a light application can be made. If the soil is already moist from recent rainfall, irrigation should be skipped. This monitoring technique helps ensure the grass receives adequate moisture without promoting the development of winter diseases.
Recognizing Signs of Stress or Disease
Distinguishing between symptoms of simple drought stress and the onset of fungal diseases is necessary for timely intervention. When St. Augustine grass suffers from winter drought, the leaf blades often fold inward, and the lawn may take on a distinct blue-gray color. Footprints left on the turf that do not spring back immediately are another sign that the grass is dehydrated and requires water.
The most common winter disease is Brown Patch, caused by the fungus Rhizoctonia solani, which thrives in cool, moist conditions. Symptoms appear as roughly circular patches of thinned, light brown grass, ranging from a few inches to several feet in diameter. Sometimes, the center of the patch recovers, leaving a distinct doughnut-shaped pattern.
A closer inspection of the affected areas may reveal a dark, water-soaked ring around the perimeter of the patch, which is the active zone of the fungus. Overwatering in the winter exacerbates Brown Patch because prolonged moisture retention in the soil and on the grass blades provides the ideal environment for the fungus. When uncertain about the lawn’s condition during the cooler months, it is safer to err on the side of less water. Fungal issues caused by overwatering are often more difficult to manage than mild drought stress.