St. Augustine grass is a warm-season turfgrass known for its dense, shade-tolerant growth and deep green color. Like all warm-season grasses, it enters a protective resting phase when temperatures drop, marking the end of its active growing season. Understanding the timing of this change is paramount for proper lawn maintenance, as summer care routines can harm the grass when it is dormant. Knowing the precise seasonal shift is the first step toward maintaining a healthy lawn year-round, especially since Texas climates vary drastically from north to south.
Defining Dormancy and Its Triggers
Dormancy is a mechanism that allows the St. Augustine grass plant to conserve energy and survive environmental stress. It indicates that the grass’s metabolism has slowed, not that the plant has died. The primary trigger for winter dormancy is the consistent drop in temperature, typically when air or soil temperatures fall below 55°F. This process is accelerated by a reduction in daylight hours, signaling the plant to prepare for colder months. Visually, the grass ceases growing and loses its vibrant color, turning a straw-like, yellowish-tan as it pulls moisture back into its crown and root system.
Geographical Timing of Dormancy Across Texas
The size of Texas creates a wide range of dormancy start times depending on the region’s climate.
North Texas
In North Texas, including areas like Dallas-Fort Worth and the Panhandle, cooler weather arrives earliest. St. Augustine grass typically enters dormancy around late October or early to mid-November, as sustained cold temperatures arrive sooner.
Central Texas
Moving south into Central Texas, encompassing cities such as Austin and San Antonio, the onset of dormancy is delayed by a few weeks. Grass in this zone usually transitions to its brown state in mid-to-late November. This area often experiences fluctuating periods where warm days interrupt the cooling trend, causing partial green-up before full dormancy.
Coastal and South Texas
Along the Coastal and South Texas regions, including Houston and Corpus Christi, the dormant period is often the shortest or most variable. Dormancy in these areas often begins in December. Due to the mild winters, the grass may only go partially dormant or experience brief periods of dormancy during sudden cold snaps, sometimes continuing to grow slowly throughout the season.
Essential Winter Preparation and Care
Mowing and Disease Prevention
Preparing St. Augustine grass for winter ensures its survival and promotes spring recovery. Before the grass enters dormancy, perform a final mowing at a slightly lower height than the summer cut. This reduces leaf mass, which minimizes the risk of fungal diseases like brown patch that thrive in cool, moist winter conditions.
Watering During Dormancy
Watering requirements change once the grass is dormant, but roots still require moisture to prevent desiccation. Water only during extended dry periods, such as once or twice a month, ensuring the soil receives a deep soak. Overwatering is counterproductive and can lead to saturated soil, increasing susceptibility to root rot and cold-weather diseases.
Fertilization Timing
Nitrogen applications should be avoided entirely once the grass is dormant, typically from December through February. Applying nitrogen during this period is wasteful since the plant cannot absorb the nutrients. Instead, a late-season application of a potassium-focused fertilizer in early fall helps harden the grass against cold stress.
Weed Control
Winter provides the best opportunity for controlling spring weeds using pre-emergent herbicides. Apply these products in the late fall when soil temperatures drop below 70°F. This timing is before the grass is fully dormant but when weed seeds begin to germinate. The application creates a protective barrier in the soil, preventing the emergence of annual winter weeds.
Spring Transition and Wake-Up
St. Augustine grass remains dormant throughout the coldest months until spring conditions signal it is safe to resume growth. The trigger for breaking dormancy is consistent soil temperatures reaching or exceeding 65°F, which allows the roots to become active and initiates the “green-up” phase.
The recovery timing follows the same north-to-south pattern as dormancy. South Texas lawns may green up as early as March. Central Texas generally starts to emerge in late March or early April, and North Texas lawns resume active growth in mid-to-late April.
As the first signs of green emerge, spring care should focus on easing the grass back into its growth cycle. The first spring mowing should occur as soon as active growth is noticeable, using the normal, higher summer height. Initial watering should be light until the grass is fully green, and the first fertilizer application should be a balanced, slow-release product applied after the grass is fully out of dormancy.