A warm-season turfgrass that grows vigorously in the heat of summertime, St. Augustine grass is a common lawn in mild subtropical regions such as Florida, Texas and California. Watering needs for it in winter are greatly diminished since its growth rate is markedly slower, even requiring much less frequent mowing maintenance. The key is conserving water and irrigating the lawn only when it needs it. Under-watering stresses the lawn, but over-watering leads to shallow roots and potential fungal problems. Don't cut St. Augustine lawns too short in winter and don't over-fertilize, if at all.
Monitor the leaf blades of the St. Augustine grass as they reveal the need for watering. Other than poking your finger into the top inch of soil to feel for moisture, the grass blades themselves either slightly curl, change color to slightly more grayish blue-green, or blades do not spring back after being walked on, leaving a matted depression. If any of these three indicators exist, consider irrigating.
Turn on the irrigation system or pull out a garden hose with sprinker head attachment when there are signs of water stress as per Step 1. Apply 1/2 to 3/4 inch water evenly to all parts of the lawn.
Calibrate your sprinkler system while you water by placing a clean, empty tuna can flat into the lawn and note how long it takes for 1/2 to 3/4 inch of water to accumulate in the can. This calibration will let you know how long you need to keep the irrigation running to provide the appropriate amount of water to the lawn.
Turn on different irrigation zones or relocate the garden hose and sprinkler head as needed to cover all areas of the St. Augustine lawn. Keep in mind the calibration numbers from Step 3 to time the watering to apply just the right amount of irrigation water to all areas of the lawn.
Irrigate again in 10 to 14 days across the cooler winter months, since the lawn is barely growing and its water needs are much lower compared to spring or summer. Extend the time in-between waterings if natural rainfall occurs and the grass blades remain emerald green and springy in texture.