Fescue is a category of cool-season perennial turfgrasses that thrive primarily in the cooler temperatures of spring and fall. When environmental conditions become too harsh, fescue initiates a natural process called dormancy. This survival mechanism allows the plant to conserve energy and water by significantly slowing or completely ceasing growth. This protects the plant’s crown and root system. Understanding the triggers of dormancy is key to maintaining a healthy fescue lawn.
Temperature and Moisture Triggers for Summer Dormancy
The onset of summer dormancy is directly tied to sustained high temperatures and a lack of available moisture. Fescue experiences significant stress when air temperatures consistently reach the upper 80s or 90s Fahrenheit. The metabolic strain is particularly severe when nighttime temperatures remain elevated, often above 75°F, preventing the grass from recovering. To minimize water loss, the grass blades shrivel and turn brown, effectively shutting down above-ground growth. This protective measure sacrifices the leaf tissue to ensure the survival of the underground crown and roots, and typically occurs during the mid-to-late summer months.
Distinguishing Dormancy from Permanent Damage
A brown lawn indicates the fescue has entered survival mode, not necessarily that it is dead. The difference between a dormant lawn and a dead one lies in the viability of the grass’s crown, the point where the roots and shoots meet. A dormant fescue plant will have a firm, intact crown, even when the blades are brown and straw-like. If you gently tug on a few brown blades and they resist the pull, the grass is dormant. Conversely, if the blades pull out easily, the grass is dead. Established fescue can survive drought-induced dormancy for three to four weeks, though this window shrinks when temperatures consistently remain in the 90s°F.
Seasonal Differences in Dormancy Periods
While summer dormancy is the most dramatic period for fescue, the grass also enters a less severe dormancy in the winter. Winter dormancy is typically initiated when soil temperatures fall consistently below 50°F and daylight hours shorten. The plant’s growth slows dramatically, reducing the need for mowing, and the color may fade to a duller green. Fescue rarely goes completely dormant in winter, and the root system often continues to develop slowly beneath the surface. This slow root growth prepares the plant for a vigorous return to growth in the spring.
Maintenance for Dormant and Recovering Fescue
During deep summer dormancy, the goal of maintenance shifts from promoting growth to ensuring the plant’s survival. This is achieved through “survival watering,” where the lawn receives minimal, infrequent moisture. Applying about a half-inch of water every two to four weeks is usually sufficient to keep the crown alive without encouraging new growth that would succumb to the heat. Avoid applying fertilizer, as the grass is not actively absorbing nutrients, and minimize heavy foot traffic because the dry blades and weakened crowns are easily damaged. When cooler temperatures return in the fall, the fescue will naturally exit dormancy, making it the optimal time for recovery steps such as aeration and overseeding.