Bermuda grass is a warm-season variety that thrives in heat but goes dormant when temperatures drop. Successfully fertilizing this turf in Oklahoma depends entirely on precise timing, aligning with the state’s climate fluctuations. Applying nutrients when the grass is dormant is wasteful, as the plant cannot absorb them, and it may promote weed growth or nutrient runoff. The fertilization schedule must align with the turf’s biological clock to ensure maximum health and recovery.
Understanding Oklahoma’s Growing Season
The signal for Bermuda grass to begin seasonal growth is the soil temperature, not the calendar date. Active growth starts only when soil temperatures consistently reach 65 degrees Fahrenheit at a four-inch depth. In Oklahoma, this threshold is typically met between late April and early May, marking the beginning of the warm-season growing period. Fertilization efforts earlier in the spring are ineffective because the plant’s roots are not ready to absorb the material.
The growing season continues through the summer and slows down as soil temperatures fall below 65 degrees, typically in the fall. Before beginning a fertilization program, conduct a soil test. This analysis reveals the soil’s current pH level and existing nutrient concentrations, such as phosphorus and potassium. Knowing the soil makeup allows you to choose the correct fertilizer blend, preventing over-application of sufficient nutrients and ensuring the grass receives what it needs.
The Essential First Feeding
The initial fertilization event, often called the “spring green-up” application, is the most important for re-establishing a healthy lawn. This first feeding should only be applied once the Bermuda grass has broken dormancy and is at least 50% green, confirming active growth and nutrient utilization. Applying fertilizer too early risks encouraging spring dead spot disease, a fungal infection that attacks weakened turf.
The goal of this first application is to promote vigorous top growth and deep green color after winter dormancy. The best choice is a complete fertilizer with a higher nitrogen ratio, such as a 4:1:2 or 3:1:2 ratio of nitrogen, phosphorus, and potassium (N-P-K). Nitrogen stimulates the rapid growth necessary for the lawn to fully recover and fill in. This application should provide about 1 pound of actual nitrogen per 1,000 square feet of turf. Use a quick-release nitrogen source, which provides an immediate boost to kickstart the lawn’s metabolism and green-up process.
Mid-Summer Maintenance Schedule
Once Bermuda grass is fully engaged in its active growing phase (typically June through August), it requires a continuous supply of nitrogen to sustain dense growth. This is the period when the grass grows fastest and consumes the most nutrients, demanding a regular maintenance schedule. Subsequent feedings should occur approximately every four to six weeks throughout the summer, depending on the fertilizer type used.
For these maintenance applications, turf professionals recommend switching to a slow-release nitrogen fertilizer source. Slow-release products allow nitrogen to be absorbed over a longer period, providing a consistent feed and reducing the risk of burning the turf in extreme summer heat. During peak summer months, Bermuda grass can tolerate and utilize higher nitrogen rates than many other turf varieties.
A primary consideration in Oklahoma is the intense heat and potential for drought during mid-summer. It is inadvisable to apply fertilizer when the turf is under heat or drought stress, even if a scheduled feeding is due. Fertilizing a stressed lawn can cause significant fertilizer burn, damaging the grass tissue. If the lawn is visibly wilting or temperatures are consistently above 95 degrees Fahrenheit, delay the application until cooler conditions return.
Preparing for Winter
The final fertilization event focuses on preparing the Bermuda grass for winter dormancy, not promoting late-season growth. This application is ideally timed between late August and early October, before the first expected hard frost. Fertilizing too late, especially after mid-October, can stimulate tender new growth highly susceptible to winter damage and fungal diseases like spring dead spot.
The composition of this late-season fertilizer must differ significantly from the high-nitrogen blends used earlier. The goal shifts from maximizing top growth to maximizing root storage and winter hardiness. Therefore, a fertilizer with a higher proportion of potassium (the “K” in N-P-K) is preferred. Potassium strengthens the plant’s cell walls, improves its ability to withstand cold temperatures, and enhances resistance to winter stress. This final application ensures the root system has sufficient carbohydrate reserves to survive dormancy and support a vigorous green-up the following spring.