St. Augustine grass is a popular warm-season turf prized for its dense, blue-green color during the summer. As seasons shift, many homeowners become concerned when their lush lawn fades to a straw-like brown. This change is often mistaken for a sign of death, causing frustration for those desiring a consistent green appearance. While the grass naturally slows down in cooler temperatures, strategic care can maximize color retention and safeguard the lawn’s health until spring. This guide outlines the steps necessary to prepare St. Augustine grass for the cold and manage its appearance during dormancy.
The Biological Reality of Winter Dormancy
St. Augustine grass is a warm-season turfgrass adapted to thrive in heat. Its vibrant green color is a byproduct of active growth, which is controlled by temperature. When air temperatures consistently drop below 55 degrees Fahrenheit, or soil temperatures fall below 68 degrees Fahrenheit, the grass triggers dormancy as a survival mechanism.
This process conserves energy and protects the root system from cold damage. The plant halts visible leaf growth and pulls essential resources back toward the stolons and roots. As chlorophyll degrades, the green tissue loses its pigment, resulting in the characteristic brown appearance. This state of rest is natural, and attempting to force vigorous growth during this period can harm the grass’s ability to survive the winter.
Critical Fall Preparation for Winter Health
Maximizing winter color and ensuring spring recovery requires preparation during late summer and fall. This preparation strengthens the grass’s structure and root density before cold weather begins. A primary step involves applying a specialized “winterizer” fertilizer four to six weeks before the first expected frost.
This final feeding must prioritize potassium (K) over nitrogen (N). Potassium strengthens the cell walls within the leaf and root tissues, improving the grass’s tolerance to cold and drought stress. Potassium also enhances the plant’s resilience against common winter diseases like Large Patch.
Mowing Height Adjustment
Gradually reducing the mowing height is another crucial preparation leading up to dormancy. Slowly lower the cutting deck from the summer height (3.5 to 4 inches) down to 2.5 to 3 inches. This shorter height reduces the grass blade mass and increases airflow to the dense stolons. Increased airflow helps prevent mold and fungus that thrive in damp, cool winter conditions.
Fall Aeration
Fall is the optimal time for aeration if a thick layer of thatch is present. St. Augustine grass is prone to thatch buildup, which blocks water and nutrient absorption. Core aeration removes small plugs of soil, breaking through the thatch layer. This ensures fertilizer, oxygen, and water penetrate deep into the root zone, allowing roots to store maximum energy before the grass fully shuts down.
Managing Appearance and Survival During Winter
Once St. Augustine grass enters dormancy, the focus shifts to ensuring survival and managing appearance. Even when dormant, the grass requires infrequent moisture to prevent winter desiccation. In the absence of rain, a deep, infrequent watering of about one-half inch every three to six weeks is sufficient.
Water only on days when the temperature is above freezing, doing so early in the morning. This allows moisture to absorb before potential evening freezes. Minimal watering keeps the root system viable without encouraging new growth that could be damaged by frost. Avoid overwatering, as it promotes fungal growth in cold, saturated soil.
Limiting foot traffic is an effective survival strategy during winter months. Dormant grass blades are brittle and easily damaged by walking or driving over them. This damage results in visible brown spots and broken turf that will not recover until spring.
For homeowners prioritizing a vibrant green appearance, the most practical solution is applying a turf colorant, or lawn dye. These specialized, non-toxic paints adhere to the dormant grass blades, restoring a natural green color immediately. This cosmetic approach is favored over traditional overseeding, as it requires no extra watering or fertilization.