St. Augustine grass is a popular warm-season turfgrass chosen for its thick, lush texture and deep green color in tropical and subtropical climates. Homeowners are drawn to its ability to create a dense lawn that thrives in high heat and partially shaded conditions. Given the increasing frequency of dry periods, the question of whether this widely used species is truly drought tolerant is important. The answer is not a simple yes or no, as its ability to withstand dry conditions depends significantly on how the grass is managed and the specific cultivar planted.
The Reality of St. Augustine’s Drought Tolerance
St. Augustine grass has moderate drought tolerance, meaning it can survive dry periods but is not efficient at water conservation. This moderate rating is due to its heat tolerance and ability to recover quickly once water is reintroduced. However, its physiological structure presents a challenge during extended dry spells. The grass is prone to surface drying because it typically develops a shallow root system when subjected to frequent, light watering. This shallow rooting means the turf quickly depletes moisture from the topsoil layer, making it highly susceptible to stress during periods without rainfall.
Recognizing the Signs of Drought Stress
Identifying the early signs of water stress allows a homeowner to intervene before permanent damage occurs. One visual indicator is a change in the leaf structure, where the normally flat blades begin to fold or curl inward along their mid-vein. This mechanism is the grass’s natural attempt to minimize water loss by reducing the leaf’s exposed surface area. Another clear sign is a shift in the lawn’s color from a vibrant green to a dull, faded blue-gray hue. The most reliable physical indicator is the “footprinting” test, where the grass remains matted down after being walked on instead of springing back upright. If footprints or mower tracks are visible for more than 10 to 15 seconds, the turf is under significant water stress and requires immediate irrigation.
Proactive Water Management for Drought Resistance
Building true drought resistance in St. Augustine grass relies on encouraging a deep, extensive root system that can access lower soil moisture reserves.
Watering Strategy
The single most effective strategy for this is a watering method known as deep and infrequent irrigation. This involves applying a substantial amount of water, typically about 1 to 1.5 inches in total, only once or twice per week. This volume of water is enough to moisten the soil to a depth of six to eight inches, which forces the roots to grow deeper in search of moisture. Conversely, daily, shallow watering trains the roots to stay near the surface, making the grass immediately vulnerable to dry conditions. The ideal time for irrigation is early in the morning, before 9:00 a.m., as this minimizes water loss to evaporation and reduces the risk of fungal disease.
Mowing Height
The height at which the grass is maintained also contributes to its resilience. Mowing St. Augustine grass at a taller height, between 2.5 and 4 inches, provides several benefits. The longer leaf blades create more shade for the soil surface, which lowers the soil temperature and significantly reduces the rate of water evaporation. The increased leaf surface area also supports better photosynthesis, producing more energy for healthy root growth.
Soil Improvement
In addition to proper watering and mowing, improving soil quality is an effective long-term measure. Core aeration helps to break up compacted soil, creating channels that allow water, air, and nutrients to penetrate deeper into the root zone. When water can move freely into the soil, the grass is better equipped to utilize rainfall and irrigation during dry periods.
Post-Drought Recovery and Long-Term Care
When St. Augustine grass turns brown during a drought, it is often entering a state of dormancy, not death, meaning recovery is possible once moisture returns. The plant sacrifices its leaves to keep the crown and roots alive. To bring a dormant lawn back, slowly reintroduce water with an initial application of about an inch per week to rehydrate the plant crowns. Once the turf shows signs of greening up, gradually return to the deep and infrequent watering schedule. Avoid applying high-nitrogen fertilizer to a recovering lawn, as this forces new growth that the weakened root system cannot support. Instead, a balanced approach, perhaps with added potassium, can support overall plant strength and future stress tolerance. If drought damage results in completely dead, large bare patches, the most reliable method for repair is to use sod patchwork or plugs. These newly installed areas require more frequent, light watering for the first few weeks to establish roots before transitioning to the long-term schedule.