When patches of green turf suddenly turn brown, yellow, or straw-colored, the appearance is often described as “burnt grass.” This discoloration is a symptom indicating severe stress or damage to the grass plants, not a single diagnosis. Identifying the specific pattern and timing of the browning is the initial step in determining the underlying issue, which could range from environmental stress to biological threats. Understanding the cause is the only way to choose an effective solution to revive the lawn.
Diagnosis Through Environmental Factors
The most common causes of widespread browning relate directly to weather and improper care practices. Drought stress, caused by a lack of sufficient water, typically results in uniform browning as the grass enters a protective dormant state. While this dormancy conserves resources, prolonged periods without water can eventually lead to plant death.
Extreme heat can also trigger this protective mechanism, particularly in cool-season grasses that struggle when temperatures exceed 80 degrees Fahrenheit. A simple test for drought dormancy involves pulling on the brown blades; if the roots hold fast, the grass is likely dormant. Mowing errors can also create a burnt appearance, especially when the grass is cut too short, an issue known as scalping. Removing more than one-third of the grass blade at a time exposes the vulnerable lower stem and shallow roots, quickly leading to browning in localized areas or on high spots of the lawn.
Chemical Exposure and Nutrient Overload
Browning can also result from the over-application or accidental spill of concentrated substances, often referred to as chemical burn. Fertilizer burn occurs when nitrogen is applied too heavily, causing accumulated salts to draw moisture out of the grass roots and blades. This damage often appears as streaks or patches where application overlapped or was unevenly distributed.
Pet urine causes a similar, highly localized burn due to its high concentration of nitrogen waste. The characteristic symptom is a dead brown patch at the center surrounded by a ring of unusually dark green grass. The nitrogen concentration in the center is toxic, while the diluted nitrogen at the perimeter acts as a potent fertilizer. Accidental spills of materials like gasoline, oil, or high concentrations of de-icing salts near driveways or sidewalks can also create distinct, sharply defined brown patches.
Identifying Pests and Fungal Diseases
Biological agents like insects and fungi require a different approach to diagnosis, as their damage patterns can mimic environmental stress. Insect pests, such as grubs, feed on the grass roots, causing brown patches that feel spongy underfoot. A key diagnostic sign for grubs is the ability to easily pull up the affected turf like a loose carpet because the roots have been severed. Chinch bugs are sap-sucking insects that inject a toxin into the grass blades, leading to irregular yellow and brown patches that often start near heat-retaining surfaces like pavement.
Fungal diseases thrive in conditions of high humidity and heat, producing distinct visual signs. Brown patch disease, caused by the fungus Rhizoctonia solani, appears as irregular brownish-yellow circles that can grow from a few inches to several feet in diameter. These patches sometimes feature a grayish border or “smoke ring” when the disease is active. Dollar Spot creates smaller, straw-colored spots roughly the size of a silver dollar, which can merge into larger damaged areas.
Steps to Revive Brown Grass
Once the specific cause of the browning is identified, recovery strategies can begin. For grass suffering from drought or heat dormancy, the immediate action is deep, infrequent watering to re-saturate the soil. Watering should aim to moisten the top six to eight inches of soil, which encourages deep root growth. In cases of fertilizer or chemical burn, the area must be flushed with water to dilute the concentrated salts and leach them out of the root zone.
Any areas where the grass is completely dead must be repaired. This process involves raking away the dead material to ensure good seed-to-soil contact before overseeding or laying sod. Long-term prevention involves proper cultural practices, such as maintaining a higher mowing height, which promotes deeper roots and better stress tolerance. Implementing a regular soil testing and fertilization schedule helps ensure the turf has the necessary nutrients to resist disease and recover from environmental challenges.