A brown lawn signals a problem, but the discoloration is a symptom rather than a specific diagnosis. Grass turns brown as a defense mechanism, indicating the plant is under stress from its environment, pests, disease, or human-induced errors. Determining the precise cause requires careful observation of the pattern, location, and nature of the damage. Because potential culprits range from natural heat waves to fungi and improper care, a systematic approach is necessary for accurate identification and response.
Causes Related to Weather and Nature
The most frequent causes of widespread browning are tied to weather patterns that push grass beyond its environmental tolerance limits. When soil moisture is depleted due to lack of rainfall, grass enters a protective state known as dormancy to conserve energy and water for survival. This mechanism involves the plant shunting resources away from the leaf blades, causing them to turn yellow or straw-colored. However, the roots and crown remain alive beneath the surface, allowing the turfgrass to recover once moisture returns. Cool-season varieties like Kentucky bluegrass are particularly prone to summer dormancy.
High temperatures can initiate browning even when water is available, a phenomenon called heat stress. Temperatures significantly above the optimum range for a specific grass type damage the plant’s cells and increase its rate of water loss (transpiration). The grass essentially overheats, and the resulting discoloration is a sign of cellular distress that can lead to death if the heat persists without relief.
In drought conditions, the grass leaves curl or fold to reduce the surface area exposed to the sun, a visible sign of water conservation. The difference between dormant grass and dead grass lies in the roots, which remain viable in a dormant lawn, ready to regrow once cooler temperatures and adequate moisture return. A simple test involves pulling the grass; if it is firmly rooted, the browning is likely due to environmental stress, not root destruction.
Damage Caused by Pests and Diseases
Browning that appears in irregular, localized patches often points toward a biological attack from insects or fungal pathogens.
White Grubs
White grubs, the c-shaped larvae of various beetles, cause damage by feeding directly on the grass roots beneath the soil surface. This root destruction starves the grass of water and nutrients, causing the turf to turn brown and thin out in irregular areas. A defining symptom of grub damage is that the affected brown turf can often be easily lifted or rolled back like loose carpet because the roots have been completely severed.
Chinch Bugs
Another insect culprit is the chinch bug, a tiny pest that feeds above ground using piercing-sucking mouthparts. These bugs extract the plant’s internal fluids and simultaneously inject a toxic substance that blocks the vascular tissue within the grass blade. This toxin prevents water movement, causing the grass to wither and die, often resulting in yellowing that progresses to reddish-brown patches. Chinch bug damage typically appears first in hot, sunny, and water-stressed areas and expands outward in irregular, spreading patterns.
Brown Patch
Fungal diseases also manifest as distinct brown patterns, with Brown Patch being one of the most common, especially in hot, humid weather. Caused by the Rhizoctonia solani fungus, this disease appears as large, circular patches of light brown or straw-colored grass that can range from a few inches to several feet in diameter. In the early morning, a subtle, dark purplish or grayish band, often called a “smoke ring,” may be visible at the perimeter of the patch where the fungus is actively spreading. Excess moisture combined with high temperatures creates the ideal environment for the fungus to thrive.
Dollar Spot
A different fungal issue is Dollar Spot, which begins as small, sunken, circular patches roughly the size of a silver dollar. The fungus is favored by periods of extended leaf wetness and is often worse in turf that is deficient in nitrogen. Examination of individual grass blades reveals small, bleached lesions bordered by a distinct reddish-brown margin. These small spots frequently merge together, creating larger, irregular areas of blighted grass.
Problems Stemming from Lawn Maintenance
Human error in lawn care practices can induce browning that mimics environmental or biological damage.
Lawn Scalping
Lawn scalping occurs when the grass is cut too short in a single mowing session. Removing too much of the grass blade exposes the inner, non-pigmented parts of the plant and stresses the crown, the plant’s growth center. This practice is damaging if more than one-third of the blade height is removed at once, and it often appears as straight brown lines or patches where the mower dipped.
Chemical Burn
Chemical burn happens from the over-application of fertilizers or misuse of herbicides. Synthetic fertilizers contain nitrogen salts that, when applied in excess, create an imbalance in the soil’s chemistry. This high salt concentration draws water out of the grass roots and leaves through osmosis, causing severe dehydration and a scorched appearance. The resulting damage often appears as streaks or checkerboard patterns corresponding to spreader overlap.
Pet Waste
Pet waste is a highly localized form of chemical burn. Dog urine contains a high concentration of urea, a nitrogen compound that acts like an intensely concentrated fertilizer. This nitrogen overload, combined with salts in the urine, causes the grass in the center of the spot to burn and die. The characteristic symptom is a patch of dead, brown grass surrounded by a ring of unnaturally dark green, vigorously growing grass.