Grass typically turns brown in the fall due to dormancy, a normal biological change. This transition is not an indication of death but is a natural, protective survival strategy turfgrasses use to endure harsh environmental conditions like freezing temperatures or drought. The grass plant effectively puts itself into a resting state by ceasing active growth and conserving the energy stored in its lower structures.
The Science Behind Seasonal Dormancy
Browning is a direct physiological result of the plant preparing for winter, driven by changing environmental cues. As the days shorten and the intensity of sunlight decreases in the fall, the grass receives signals that trigger a reduction in photosynthesis. This process is further accelerated by the consistent drop in both air and soil temperatures.
The most noticeable sign of this slowdown is the cessation of chlorophyll production, the pigment responsible for the green color. Similar to how deciduous trees change color, the grass begins to break down the existing chlorophyll molecules. As the green pigment disappears, the underlying yellow and brown pigments become visible, resulting in the characteristic straw-brown color of a dormant lawn.
Dormancy is a protective state where the plant redirects its limited energy resources away from the leaf blades and into the crown and root system. The plant focuses on storing nonstructural carbohydrates, which act as energy reserves, in these lower structures. This shift ensures the plant’s core survival mechanisms are sustained through the winter, allowing the grass to endure freezing temperatures and limited water availability.
How Grass Types Respond to Cold
The degree and timing of browning depend heavily on the specific type of grass, categorized as either warm-season or cool-season species. Warm-season grasses, such as Bermuda, Zoysia, and St. Augustine, thrive in high temperatures and are highly sensitive to the first frost. These grasses will typically turn a uniform, deep brown very quickly when temperatures consistently drop below 50–60°F.
Warm-season varieties enter a deep, predictable dormancy as a survival mechanism against the cold. They completely shut down top growth and rely entirely on their underground structures for survival throughout the winter.
Cool-season grasses, including Kentucky Bluegrass and Fescues, respond differently to the cold onset of autumn. These species are adapted to cooler conditions and continue to grow actively well into the fall, sometimes remaining green throughout the winter in milder climates. They only enter true dormancy if temperatures become extremely cold or if they face prolonged, severe drought conditions.
Dormant or Dead How to Tell the Difference
While a uniformly brown lawn is usually a sign of normal dormancy, it is important to distinguish this protective state from actual death or severe damage. Dormant grass will typically exhibit a consistent, even browning across the entire turf area, indicating a systemic response to the cold. Patchy or circular brown spots, however, often suggest localized issues such as disease, pests, or uneven soil conditions.
A simple diagnostic technique is the “tug test” on a small patch. If the grass is merely dormant, the root system remains alive and firmly anchored in the soil, resisting a gentle pull. If the grass blades pull out easily from the soil without resistance, it suggests the root system has failed and the grass is likely dead.
Another visual clue is the condition of the crown, the small area at the base of the plant where new growth originates. In dormant grass, this crown tissue will still appear firm and may retain a slight white or pale green color. If the crown is brittle and completely brown or gray, the plant has likely died.
Winter Survival and Spring Recovery
During winter, the grass survives by relying on the energy stored in its roots and crown structures. These stored nonstructural carbohydrates, accumulated during the fall, act as antifreeze by increasing the solute concentration within the plant cells. This process lowers the freezing point of the plant’s internal fluids, protecting the living tissue from lethal intracellular ice formation.
The crown, the protected growing point, maintains a lower moisture content as the plant acclimates to the cold. This physiological change further enhances the plant’s ability to resist freezing and desiccation injury throughout the winter. The grass is essentially in a state of suspended animation, minimizing all metabolic activity.
Spring recovery begins when the soil temperature consistently rises, typically reaching the low to mid-50s Fahrenheit for cool-season grasses. These warmer conditions trigger a process called de-acclimation, where the plant begins to mobilize its stored carbohydrate reserves. This stored energy fuels the first burst of new growth, allowing the grass to rapidly produce new, green shoots and resume active photosynthesis.