St. Augustine grass is a popular warm-season turf known for its coarse texture, dense growth habit, and vibrant green color, making it a favorite for lawns across the southern United States. Because this grass is a vigorous grower, it demands a significant and consistent supply of nutrients to maintain its health and appearance. The timing of fertilization is the most impactful factor in the lawn’s well-being, as it must align precisely with the active growth cycle. Applying fertilizer at the wrong time wastes product, stresses the grass, and can encourage the growth of weeds.
Prerequisites for Spring Fertilization
The first fertilizer application of the year should occur only after St. Augustine grass has fully emerged from winter dormancy and is actively growing. This timing is based on environmental conditions, not a calendar date, specifically the soil temperature. The grass utilizes nutrients efficiently once the soil temperature, measured at four inches, consistently reaches 65 to 70 degrees Fahrenheit.
A visible indicator that the lawn is ready is the “spring green-up,” when grass blades transition from dormant brown to actively growing green. Fertilizing too early is counterproductive because the roots cannot absorb the nutrients before the temperature threshold is met. Unused nitrogen can leach into the environment or promote the growth of cool-season weeds. Delaying application ensures nutrients fuel deep root development and active turf growth.
Mid-Season Feeding Strategy
Once the initial spring application is complete, St. Augustine grass requires follow-up applications to sustain peak growth and color through the summer. The frequency of these mid-season feedings depends on the high demand for nitrogen during the active growing period, which spans late spring through mid-summer. Lawns thrive when nutrients are supplied consistently to prevent color fading and maintain density.
Most maintenance programs recommend a feeding interval of six to eight weeks during the peak heat of the growing season. This consistent application ensures the grass has the energy to withstand summer stresses like heat and drought. Monitoring the lawn for signs of fading color or slowed growth indicates the need for the next application within this two-month window. This strategy provides a steady supply of nutrients, supporting continuous growth.
Preparing the Lawn for Winter
As the season progresses, the focus shifts from promoting vigorous growth to preparing the turf for dormancy. The final fertilizer application of the year is timed to boost root health and enhance cold tolerance without encouraging new leaf growth. This last feeding should occur roughly six weeks before the first expected frost date for your region.
A general rule is to cease nitrogen application when nighttime temperatures consistently drop below 60 degrees Fahrenheit. Applying nitrogen too close to cold weather stimulates shoot growth that is susceptible to frost damage. The goal of this late-season timing is to allow the grass to “harden off,” storing energy in its root system for a healthier transition into and out of dormancy.
How Fertilizer Type Alters the Schedule
The type of fertilizer used directly influences the frequency of the mid-season feeding schedule. Fertilizers are categorized as either quick-release or slow-release, referring to how rapidly the nitrogen component becomes available to the grass. Quick-release formulations are water-soluble and provide a rapid green-up within days, but their effects are short-lived.
If you choose a quick-release product, the mid-season application interval must be shorter, typically four to six weeks, to maintain consistent color and growth. Conversely, slow-release fertilizers deliver nutrients gradually over an extended period, sometimes for up to three to six months. Utilizing a slow-release product allows the feeding interval to be extended to eight to ten weeks, reducing the number of applications needed.