The question of when grass turns green again after winter dormancy is common, but the answer is not a single month on the calendar. The exact timing is highly variable, depending on a combination of biological factors, geographic location, and the specific variety of grass planted. This reawakening of the lawn is a complex physiological process, not triggered by a date, but by environmental conditions meeting the minimum requirements for the grass to resume active growth. Understanding these underlying factors helps homeowners predict and prepare for the spring green-up.
The Biological Trigger: Soil Temperature
The true signal for grass to break winter dormancy is not the air temperature, but the temperature of the soil beneath the surface. While a few warm, sunny days may temporarily increase the air temperature, the soil warms up far more slowly and consistently. This sustained warmth is what the grass roots require to activate the cellular processes needed for growth.
The roots of the turfgrass plant begin to push new growth when the soil reaches a certain temperature range, typically measured at a depth of four inches. For cool-season grasses, the green-up process starts when the soil temperature is consistently between 40°F and 55°F. Warm-season grasses require a much higher threshold, generally needing the soil to reach a sustained 65°F or higher. The existing brown blades do not actually turn green; instead, the roots generate entirely new, green shoots that emerge from the crown of the plant.
How Geography Influences Green-Up Timing
Since soil temperature is the primary factor, a lawn’s geographic location significantly influences the calendar month when dormancy breaks. Regions in the southern United States and the Deep South, which experience milder winters, are the first to see the green return. In these warmer climates, grass may begin to break dormancy as early as February or March.
Moving north into the Mid-Atlantic and Midwest regions, the process is delayed due to longer periods of cold soil. Here, the green-up generally occurs later, often starting in early to mid-April. In the northern US and New England, where frost penetrates deeply and persists longer, the soil takes the longest to warm up. Lawns in these colder zones typically do not begin to turn green until late April or even early May.
Cool-Season vs. Warm-Season Grass Differences
The species of grass planted is the second major determinant of green-up timing, regardless of geographic location. Turfgrasses are broadly categorized into two types based on their preferred growing season.
Cool-Season Grasses
Cool-season grasses, which include varieties like Kentucky Bluegrass, Tall Fescue, and Perennial Ryegrass, are best suited for northern climates and the transition zone. These types are the first to green up in the spring because their root growth is optimized for lower soil temperatures.
Warm-Season Grasses
Warm-season grasses, such as Bermuda, Zoysia, and St. Augustine grass, are primarily grown in the South and thrive in hot summer weather. These grasses remain dormant and brown much longer, often waiting until the soil reaches the higher temperature threshold before they show significant signs of life.
Essential First Steps After Dormancy Breaks
Once the first hint of green appears, the lawn is actively growing and ready for initial maintenance steps. The very first action should be to clear away any debris that accumulated over the winter, such as fallen leaves, sticks, or matted dead grass. A light raking helps remove this material, which allows sunlight and air to reach the soil surface, promoting faster warming and healthier new growth.
Homeowners should delay the first fertilizer application until the grass is actively growing and has been mowed at least once. Applying fertilizer too early, especially to warm-season grass, can overstimulate the plant before it is fully ready and may encourage weed growth instead of turf growth. The first application often includes a pre-emergent herbicide, which is timed specifically to prevent the germination of spring weeds like crabgrass.