The question of whether Bermuda grass and Fescue grass can grow together is a common one for homeowners in the “transition zone,” where climates shift between hot summers and cold winters. Bermuda grass is a warm-season turf, thriving in temperatures between 75°F and 95°F, making it well-suited for southern regions. Fescue, particularly tall fescue, is a cool-season grass, with its optimal growth range occurring between 55°F and 75°F, making it popular in northern climates. While the two grasses can physically coexist, their fundamental biological differences create a constant conflict that prevents a uniform, high-quality lawn. This article will explore the incompatibilities of these two turf types and offer practical strategies for managing or resolving a mixed stand.
Understanding the Fundamental Differences
The primary conflict between these two turfgrasses stems from their temperature preferences and differing photosynthetic mechanisms. Bermuda grass utilizes the C4 photosynthetic pathway, which is highly efficient in intense light and high temperatures, allowing it to flourish during the hottest summer months. Conversely, Fescue relies on the C3 pathway, performing best in the milder temperatures of spring and fall. This biological distinction means that when one grass is actively growing and robust, the other is typically stressed or dormant.
Their methods of spread are another point of divergence. Bermuda is an aggressive spreader, relying on both above-ground runners (stolons) and below-ground stems (rhizomes) to rapidly colonize bare soil. This expansive growth habit allows it to form a dense, durable turf quickly. Fescue, conversely, is a bunch-type grass, spreading only through vertical shoots (tillers), which limits its ability to self-repair or aggressively fill in large areas.
The light requirements also dictate their suitability for different parts of a yard. Bermuda demands full, direct sunlight for at least six to eight hours daily to maintain density and color. Fescue exhibits a much higher tolerance for shade, making it a viable option for lawns with mature trees or varying light exposure throughout the day.
The Consequences of Mixed Growth
When these two incompatible grasses are forced to share a space, the result is a continuous cycle of competition and aesthetic compromise. During the summer, Bermuda grass becomes highly competitive. Its aggressive stolons and rhizomes quickly invade and strangle the bunch-type Fescue, which is already weakened by the heat. The Fescue struggles to survive under the Bermuda canopy and will thin out, often leaving noticeable patches of the coarser warm-season grass.
The most visible conflict is the dormancy clash that creates a patchy, non-uniform appearance year-round. As temperatures drop in late fall, Bermuda grass enters dormancy, turning a straw-brown color that persists through the winter. Fescue, being a cool-season grass, remains green during the winter months, highlighting the brown patches of dormant Bermuda.
When summer arrives, the situation reverses. Fescue often enters a semi-dormant state to cope with high heat, sometimes turning a dull green or brown. Bermuda is simultaneously at its peak color and density, resulting in a lawn that is visually inconsistent throughout both the cool and warm seasons. The fine-to-medium texture of Bermuda contrasts sharply with the broader blades of Fescue, resulting in a visibly non-uniform surface texture.
Maintaining a Mixed Stand
Homeowners who inherit a mixed lawn face the challenge of providing maintenance that meets the conflicting needs of both grass types.
Mowing Height
Mowing height requires a difficult compromise. Bermuda performs best when cut low (1 to 2 inches), while Fescue thrives at a higher cut (3 to 4 inches) to promote root depth and shade the soil. A compromised mowing height, typically around 2.5 inches, is often too high for Bermuda to maintain density and too low for Fescue to survive summer stress effectively.
Watering Schedule
The watering schedule also presents a dilemma. The deep and infrequent irrigation required for Fescue in the summer strongly encourages the aggressive summer growth of Bermuda. To keep Fescue alive during the hottest months, supplemental water is needed. The most effective strategy for a mixed stand is to apply the minimum amount of water necessary to prevent Fescue from dying, thereby suppressing the Bermuda’s vigor slightly.
Fertilization Timing
Fertilization timing must be carefully managed to avoid accelerating the dominance of one grass over the other. Applying nitrogen fertilizer in the spring and fall favors Fescue, as this is its peak growth period, helping it to thicken before and after the summer stress. Fertilizing during the summer, however, exclusively benefits the warm-season Bermuda, fueling its aggressive spread and further weakening the Fescue.
Strategies for Favoring One Grass Type
If the goal is to transition the mixed lawn into a single, uniform turf, specific cultural practices and selective chemical applications can be employed.
Favoring Fescue
To encourage Fescue dominance, the mowing height should be raised to its highest recommended level, ideally 4 inches, during the Bermuda’s active growth season. This tall Fescue growth shades the soil, which effectively limits the sunlight necessary for Bermuda to thrive, suppressing its growth. Chemical control involves using selective herbicides that target warm-season grasses without harming the cool-season Fescue. Products containing active ingredients like fluazifop or topramezone can be applied during the spring and fall to suppress or eliminate the Bermuda. Multiple applications are typically required due to Bermuda’s tenacious nature and its extensive network of rhizomes and stolons.
Favoring Bermuda
To favor Bermuda and eliminate Fescue, the opposite cultural practices should be implemented, including frequent mowing at a low height (1 to 1.5 inches) and aggressive summer fertilization. This low-cut approach stresses the Fescue, while the summer nitrogen feeds the Bermuda, allowing it to quickly outcompete and colonize the remaining Fescue clumps. Selective herbicides, such as those containing the active ingredient dicamba or mecoprop, can be used to target the cool-season Fescue, especially during its active growth periods in the cooler months.
Full Renovation
For a complete and rapid transition, the most definitive solution is full renovation. This requires the use of a non-selective herbicide, such as glyphosate, to kill all existing grass. This should be done when the targeted grass is actively growing to ensure the chemical is fully transported throughout the plant’s root system. After the area is cleared, the homeowner can then re-establish the desired monoculture lawn through seeding, sodding, or sprigging during the optimal planting window for the chosen grass type.