The sudden appearance of a brown lawn during a hot summer is a common sight that often leads homeowners to believe their grass has died. This discoloration, however, is not always a sign of death but rather a survival mechanism triggered by environmental stress. Understanding the difference between a natural protective state and genuine damage is the first step toward maintaining a healthy lawn.
Dormancy: The Grass’s Survival Strategy
The physiological process that causes grass to turn brown is known as estivation, a form of dormancy induced by drought and high temperatures. During this protective shutdown, the plant conserves water and energy reserves. Growth ceases entirely, and the grass blades stop producing chlorophyll, the pigment responsible for their green color, leading to the familiar straw-like appearance.
The grass remains alive because it retains a healthy, hydrated crown, which is the white or creamy-colored base of the plant where the roots and shoots meet. Cool-season grasses, such as Kentucky bluegrass and fescue, enter this state when temperatures consistently exceed 95°F and soil moisture is depleted.
An established lawn can typically survive in this drought-induced dormancy for approximately three to four weeks. If extreme heat persists with temperatures in the 90s, this survival window may shorten to as little as two to three weeks. You can confirm dormancy by performing a simple tug test; if the blades resist pulling and remain anchored, the crown and root structure are still intact and viable.
When Browning Signals Damage or Disease
Browning that appears in irregular or isolated patches, rather than uniformly across the entire lawn, often signals a problem beyond simple dormancy. Fungal diseases thrive in summer conditions, with two common culprits being brown patch and dollar spot. Brown patch creates large, irregular circles that can grow up to several feet in diameter, causing the grass blades to develop lesions with dark borders and tan centers.
Dollar spot is visually distinct, manifesting as small, straw-colored circles roughly the size of a silver dollar. Examining the individual grass blades reveals characteristic hourglass-shaped lesions, distinguishing this fungal infection from simple drought stress. Both diseases can spread rapidly in high heat and humidity, particularly when the grass remains wet for extended periods.
Insect infestations also cause patterned browning that mimics drought. Grubs, the larvae of various beetles, feed directly on grass roots, effectively severing the plant from its water source. This damage causes the affected areas to feel spongy underfoot, and the brown grass can be easily lifted or rolled back like a loose piece of carpet.
Chinch bugs cause damage resembling drought, but the grass remains rooted. These insects pierce the grass blades and suck out the plant fluids, injecting a toxic substance that blocks water movement. This results in irregular, yellow-brown patches that begin near sidewalks or driveways and gradually spread outward.
Steps for Recovery and Future Prevention
Reviving a dormant lawn begins with deep, infrequent watering to rehydrate the crowns without encouraging shallow root growth. Aim to apply 1 to 1.5 inches of water per week, delivered in a single session or two, ideally during the early morning hours before 9 a.m. This timing minimizes water loss from evaporation and reduces the duration that the grass blades remain wet, which helps deter fungal growth.
Adjusting your mowing practices is an effective preventative measure against summer stress. Raise the mower deck to its highest setting, typically 3 to 4 inches for cool-season varieties, to encourage a deeper root system and allow the taller blades to shade the soil. Shading the ground helps keep the crown cool and significantly reduces moisture evaporation.
Avoid applying heavy nitrogen fertilizer to cool-season grass during peak summer heat, as this can force growth when the plant is trying to conserve energy, leading to fertilizer burn. If feeding is necessary, apply a slow-release product on a morning when temperatures are relatively moderate.