The sight of a browning lawn in the summer heat often causes concern for homeowners, but this straw-colored appearance is a temporary survival strategy known as dormancy. Dormancy is a natural, protective mechanism that allows the plant to conserve energy and water when faced with environmental stresses, such as prolonged drought or extreme heat. The grass does not die; instead, it intentionally slows its metabolic activity and growth, sacrificing the green blades to protect the most vital parts of the plant. This response ensures the lawn can recover and green up again once favorable growing conditions return.
The Two Categories of Lawn Grasses
The likelihood of a lawn entering summer dormancy depends on its fundamental grass type, categorized based on optimal growing temperatures. Cool-season grasses, such as Kentucky bluegrass, fescue, and perennial ryegrass, grow best in cooler conditions, typically between 60°F and 75°F. These varieties experience their peak growth in the spring and fall, but they readily enter summer dormancy when faced with high temperatures and insufficient moisture. Their inability to thrive in the heat is the primary reason for browning lawns during July and August.
Warm-season grasses, like Bermuda, Zoysia, and St. Augustine grass, have a much higher temperature preference, actively growing when temperatures are between 80°F and 95°F. These grasses are adapted to summer heat and are less likely to enter heat-induced dormancy. Instead, warm-season varieties enter dormancy when temperatures consistently fall below 60°F, causing them to turn brown during the winter months. Understanding this distinction is the first step in managing a lawn’s reaction to summer weather.
Biological Triggers and Mechanisms of Dormancy
For cool-season grasses, dormancy is triggered primarily by a combination of high soil temperatures and drought stress. When the plant senses a lack of water and excessive heat, it initiates a physiological shutdown to prevent desiccation. The grass stops diverting energy to new leaf tissue production, which is the most water-intensive part of the plant. This cessation of growth is often visible when the blades turn brown and crispy.
The plant significantly reduces photosynthesis because this process requires open stomata for carbon dioxide uptake, which leads to water loss. Instead of using energy for growth, the grass focuses resources on protecting the meristematic tissue, located in the crown near the soil line. The crown and the root system remain alive and hydrated, functioning as a reservoir of energy and life until moisture returns. This mechanism can allow many cool-season species, such as Kentucky bluegrass, to survive four to six weeks of drought conditions without severe damage.
Distinguishing Dormancy From Grass Death
A brown lawn does not automatically mean the grass is dead; simple tests can help determine its status. The most reliable method is the “tug test,” where a small handful of brown grass is gently pulled. If the grass resists the pull and remains firmly anchored in the soil, the root system is intact, indicating dormancy. However, if the grass blades easily lift out of the ground with no resistance, the roots have likely failed, and the turf is dead.
Another diagnostic step involves examining the crown, the white or light-colored tissue at the base of the plant. By digging up a small section of turf and inspecting this area, a homeowner can check for signs of life. A dormant plant will have a firm, intact crown, often with healthy, white or light brown roots clinging to the soil. Conversely, a dead plant will have a dark, shriveled, or mushy crown and weak, decayed roots that crumble easily.
Recommended Care During Summer Dormancy
Once dormancy is confirmed, management shifts from promoting growth to ensuring the survival of the plant’s crown and roots. Minimize all stress on the lawn, including drastically reducing foot traffic to prevent crushing the fragile, non-growing tissue. Mowing should be completely stopped, as cutting the already stressed blades further depletes the plant’s energy reserves and increases the risk of plant death.
For lawns that have been dormant for several weeks, “survival watering” is recommended to prevent the crown from desiccating. This involves applying a very light amount of water, typically about a half-inch, every two to three weeks. This minimal water application is not intended to encourage the grass to green up, which would break dormancy and increase water demand, but only to keep the crown alive until weather conditions improve. Fertilization should also be paused entirely, as the dormant plant cannot utilize the nutrients, and the application may cause unnecessary stress.