Bermuda grass is a popular warm-season turf known for its resilience and deep green color throughout the summer months. As temperatures drop in the fall, this grass naturally transitions, losing its vibrant hue and turning a straw-colored brown. This seasonal change is a completely normal, protective state called winter dormancy. The timing of this spring transformation is not tied to a specific calendar date but rather to precise biological signals from the environment.
Understanding Bermuda Grass Dormancy
Dormancy is a survival mechanism that allows warm-season grasses to endure cold temperatures. When the soil temperature consistently falls below approximately 55°F, the plant begins to slow its metabolic activity dramatically. The grass conserves energy in its underground structures, such as the rhizomes and stolons. During this period, the plant stops producing chlorophyll, the green pigment responsible for photosynthesis, which causes the visible leaf blades to turn brown and dry out. The grass is merely resting in a state of suspended growth, waiting for the return of favorable conditions.
The Critical Soil Temperature Trigger
The single most important factor controlling spring green-up is the temperature of the soil, not the air. Bermuda grass requires a sustained soil temperature between 60°F and 65°F at a depth of four inches before it will actively break dormancy. This consistent warmth is necessary to restart the metabolic processes within the plant’s crown and root system.
A few warm, sunny days in late winter may cause the air temperature to spike, but the soil retains cold much longer, preventing premature growth. The grass will not commit to green-up until the root zone is warm enough to sustain new shoot and leaf development. Homeowners can monitor this threshold by using an inexpensive soil thermometer inserted four inches deep into the lawn.
Once the soil temperature remains consistently within this range for several consecutive days, the grass begins to draw on its stored carbohydrates. This energy fuels the production of new green shoots that emerge from the crown of the plant, signaling the end of dormancy. The process is gradual, as the turf requires stable warmth to ensure it does not exhaust its reserves only to be damaged by a late-season frost.
Regional and Environmental Influences on Timing
While the 60°F to 65°F soil temperature requirement is universal for the species, the calendar date when this occurs varies significantly by location. In the Deep South, where winter temperatures are milder, this threshold may be reached as early as late March. Areas further north, particularly those in the Transition Zone, typically see green-up delayed until late April or even mid-May.
Local environmental conditions, known as microclimates, can also significantly alter the timing within a single neighborhood. Areas of the lawn that receive full, unobstructed sunlight warm up much faster than those in heavy shade. A lawn section next to a south-facing concrete driveway will likely green up earlier because the pavement absorbs and radiates heat back into the soil. Conversely, areas under large shade trees or on north-facing slopes can have soil temperatures several degrees cooler, delaying their green-up by weeks compared to the sunniest parts of the yard.
Post-Dormancy Care: Encouraging Strong Green-Up
Once the first signs of green are evident, homeowners can take specific steps to accelerate the full recovery of the lawn. The initial action is often the first mowing, frequently referred to as scalping. This involves setting the mower height low to remove the remaining brown, dormant leaf tissue and thatch.
Scalping allows more sunlight to penetrate the soil surface, further accelerating the soil warming process and encouraging more vigorous new growth. The old brown clippings should be collected and removed to prevent smothering the emerging green shoots.
Watering is important during the spring transition, especially if the weather is dry. While the grass is still waking up, it needs consistent moisture to support the sudden burst of new shoot and root growth. Aim to provide about one inch of water per week, factoring in any rainfall.
Fertilization should be timed carefully, as applying nitrogen too early can promote weak growth that is susceptible to a late frost. The first application of a nitrogen-based fertilizer is best delayed until the lawn is at least 50% to 75% green. This ensures the grass is actively growing and can efficiently absorb the nutrients for a strong start to the season. The timing for pre-emergent weed control is an exception, as it is often applied when soil temperatures reach 55°F, which is just before the grass begins its green-up.