Centipede grass is a popular warm-season turf, valued for its low maintenance requirements. While it thrives in the Southern climate, its specific nutritional needs are distinct, making proper fertilization a delicate process. Using the wrong fertilizer or applying it incorrectly can severely stress or damage the lawn. This guide outlines the unique requirements of centipede grass to help homeowners select the best fertilizer.
Understanding Centipede Grass Nutritional Requirements
Centipede grass has the lowest nitrogen (N) requirement of all common turfgrasses, which is the primary factor dictating fertilizer selection. Too much nitrogen encourages excessive, rapid growth that can lead to “centipede decline” due to shallow root systems and increased susceptibility to disease and cold damage. The total annual application of nitrogen should be limited to between one and two pounds per 1,000 square feet, with the lower rate often sufficient for lawns on clay soil.
Phosphorus (P) is rarely needed in established centipede lawns, and its over-application can be detrimental. A buildup of phosphorus interferes with the grass’s ability to absorb iron, leading to a yellowing of the leaves known as chlorosis. Potassium (K) is generally needed in moderation to help with water regulation, disease resistance, and winter hardiness.
Centipede grass prefers acidic soil, ideally maintaining a pH range between 5.0 and 6.0. This stands in contrast to many other turf varieties that prefer a more neutral pH. Applying lime, often used to raise the pH for other grasses, is highly damaging to centipede grass unless a soil test specifically indicates a need to raise an overly low pH.
Iron is often more important than nitrogen for maintaining a desirable green color without triggering excessive growth. When the soil pH is too high (above 6.0) or phosphorus levels are elevated, iron availability decreases, causing the grass to yellow despite adequate nitrogen. An application of iron can quickly restore the green color by supporting the grass’s chlorophyll production.
Selecting the Right Fertilizer Ratios and Types
The unique nutritional demands of centipede grass necessitate the selection of fertilizers with a specific chemical composition. The ideal NPK (Nitrogen-Phosphorus-Potassium) ratio should reflect the low nitrogen and near-zero phosphorus needs. Recommended ratios often include formulas like 15-0-15, 16-0-8, or 5-5-15, all of which prioritize a low nitrogen content relative to potassium and minimize or eliminate phosphorus.
Slow-release nitrogen sources are strongly preferred for centipede grass over quick-release options. These fertilizers, often containing components like sulfur-coated urea or polymer-coated urea, prevent the sudden surge of growth that can lead to centipede decline and thatch buildup. This constant, low-level feeding provides sustained nutrition and reduces the risk of burning the turf.
Because iron is important for color, many centipede-specific fertilizers include an iron supplement. Alternatively, homeowners can apply iron sulfate (ferrous sulfate) or chelated iron products separately. Applying two ounces of ferrous sulfate mixed in three to five gallons of water per 1,000 square feet can enhance the color, and the effect is usually visible within 24 hours.
Fertilizers are available in both granular and liquid forms, with granular being the most common choice for macro-nutrient applications. Liquid iron supplements are particularly effective for rapid color correction because the nutrients are quickly absorbed through the leaves, known as foliar absorption. Avoid using general-purpose “weed and feed” products, as they are often formulated with high nitrogen levels or herbicides that can be fatal to centipede grass.
Seasonal Timing and Application Guidelines
Before applying any fertilizer, a soil test must be performed to accurately determine the existing pH and nutrient levels. This test provides scientific data to confirm if phosphorus or lime is needed, preventing costly mistakes from unnecessary applications. Soil test results are the only reliable way to tailor the fertilizer selection to the lawn’s specific deficiencies.
The timing of the initial fertilizer application is critical to avoid promoting new growth that could be damaged by a late frost. The first feeding should occur in late spring, after the grass has completely greened up and after it has been mowed at least once or twice. This typically falls between mid-May and early June, when soil temperatures have consistently reached 65 degrees Fahrenheit at the four-inch depth.
Centipede grass generally requires only one to two fertilizer applications per year due to its low nitrogen needs. The total annual nitrogen applied should not exceed one to two pounds of actual nitrogen per 1,000 square feet. If a second application is deemed necessary for growth or color, it should be made in mid-summer, typically around June or July.
A final application of nitrogen must be avoided in the late season to prepare the grass for winter dormancy. All nitrogen feeding should stop six to eight weeks before the first expected frost, usually by mid-to-late August. However, this period is an appropriate time to apply a high-potassium, nitrogen-free fertilizer if a soil test indicates a potassium deficiency, as this nutrient enhances winter hardiness.