When a lawn turns brown in the colder months, many homeowners assume the grass has died. This change from lush, green turf to a straw-like color is often misunderstood. However, the appearance of a brown lawn in winter is usually a survival mechanism, not a sign of permanent loss. The actual condition of the grass plant reveals a range of possible causes, from natural cycles to severe environmental impact or disease. Understanding the specific reason for the color change is the first step toward effective diagnosis and recovery once warmer weather returns.
Distinguishing Dormancy From Death
The most important distinction to make when facing a brown winter lawn is whether the grass is merely dormant or truly dead. Dormancy is a natural, temporary state where the grass conserves energy by slowing growth and drawing nutrients down to the root crown to survive cold or dry conditions. In this state, the grass blades are brown, but the crown—the growing point located just above the soil line—remains alive, firm, and often white or light-colored.
To determine the status of the plant, homeowners can perform a simple ‘tug test’ on a small patch of the brown turf. If the grass resists being pulled and the roots are securely anchored to the soil, it is likely dormant and will revive when conditions improve. Conversely, if the grass pulls out of the ground easily, and the roots appear brittle, gray, or dark brown, the plant is dead. Dormant grass typically displays a uniform brown color, whereas dead grass often appears in irregular, scattered patches, suggesting a localized problem.
Environmental Stressors
Widespread grass death in winter, often grouped under the term “Winter Kill,” is frequently caused by severe weather-related environmental stressors. One common factor is desiccation, which occurs when cold, dry winds constantly pull moisture from the grass blades while the frozen ground prevents the roots from taking up replacement water. This persistent drying causes the grass to die from dehydration, particularly in areas exposed to prevailing winds or lacking protective snow cover.
Another significant cause is crown freeze injury, where the plant’s sensitive growing point is physically damaged by ice crystal formation. This injury, sometimes called crown hydration, happens when the grass crown is saturated with water and then rapidly exposed to extremely low temperatures. The formation and enlargement of ice crystals outside the plant cells draw water out, causing cell dehydration and ultimately the death of the crown.
Prolonged ice sheet suffocation presents a further threat, typically when rain or melting snow freezes into a thick, continuous layer over the turf. Even semi-dormant grass still respires, but this thick ice layer limits the exchange of gases. The lack of oxygen (anoxia) and the buildup of toxic gases beneath the ice can kill the turf. The duration of the ice cover is a greater factor in damage than the initial cold itself.
Cold-Weather Fungal Diseases
Beyond environmental damage, certain cold-weather fungal pathogens thrive under the specific conditions of late fall and winter, leading to disease. The most common of these is Snow Mold, which appears in two primary forms: Gray Snow Mold (Typhula blight) and Pink Snow Mold (Microdochium patch). Both types become active under a blanket of snow, especially when the ground has not completely frozen, trapping moisture and creating a humid environment perfect for fungal growth.
Gray Snow Mold mainly damages the grass blades, appearing as circular, straw-colored patches that are matted and covered with grayish-white fungal threads. Pink Snow Mold is more aggressive because the fungus can kill the grass crown and roots. This type of mold forms whitish-pink patches, often less than six inches across, and can continue to spread in cool, wet conditions even after the snow has melted.
Localized External Damage
Damage to winter grass may also be highly localized, often stemming from specific external factors. One frequent culprit is salt damage, resulting from the use of de-icing salts on nearby sidewalks and driveways. Salt runoff and spray are absorbed into the soil, where they draw moisture away from the grass roots, causing the grass to die from desiccation and increasing soil salinity. This damage is typically concentrated along pavement edges where salt application is heaviest.
Foot traffic poses a significant risk to dormant or frozen grass. When the grass crown is frozen and brittle, walking on it crushes the plant cells, which are incapable of repairing themselves until the thaw. These localized pressure points result in dead, visible trails that become apparent in the spring. Small mammals also cause damage, particularly voles, which create shallow, visible runways beneath the snow cover while feeding on grass blades. Moles, though active year-round, can create mounds and tunnels that disrupt the root systems beneath the turf.