Whether grass can grow in 50-degree weather is a common question for homeowners anticipating spring or fall. The answer depends entirely on the type of grass and whether you are measuring the air or the soil temperature. Some grass types begin to stir at this temperature, while others remain completely dormant. The 50°F mark is a significant biological threshold that signals a change in season for turfgrass, often prompting decisions about lawn care timing.
Understanding the Difference Between Soil and Air Temperature
The temperature surrounding the grass blades is not the primary factor governing growth. Metabolic processes like root activity and nutrient uptake happen underground, meaning the soil temperature is the true driver of lawn growth. The soil acts like an insulator, changing temperature much more slowly than the air above it.
This insulating effect means that a 50°F air temperature will not immediately translate to the same soil temperature. In spring, the soil remains cold longer, delaying the start of the growing season even after the air warms. Conversely, soil retains heat longer in the fall, allowing grass to continue growing after the air cools. To determine the lawn’s readiness, a soil thermometer is necessary to measure the temperature at a depth of a few inches.
Growth Thresholds for Cool-Season and Warm-Season Grasses
Whether grass will grow at 50°F depends entirely on its category. Cool-season and warm-season grasses have vastly different temperature requirements for root and shoot activity. Cool-season grasses, such as Kentucky Bluegrass, Fescue, and Ryegrass, are active during the cooler months of spring and fall.
Cool-season grasses begin to emerge from dormancy and initiate root growth when soil temperatures consistently reach the 50°F to 65°F range. At 50°F, roots actively repair winter damage and absorb nutrients, even if visible blade growth is minimal. This 50°F mark is also the minimum threshold for the germination of many cool-season grass seeds. Optimal shoot growth occurs in the warmer soil range of 60°F to 75°F.
Warm-season grasses, including Bermuda, Zoysia, and St. Augustine, require much higher temperatures and will not grow at 50°F. These grasses are found in southern regions and thrive when temperatures are between 75°F and 90°F. When soil temperatures drop to 50°F, warm-season grasses enter dormancy, turning brown until the warmth returns. Significant growth requires soil temperatures to be consistently above 65°F for the plant to break dormancy.
Practical Lawn Care When Temperatures Are Low
The 50°F soil temperature threshold is a significant marker for timing several important lawn care tasks. For cool-season grass, this temperature signals the start of the pre-emergent herbicide application window. Applying a pre-emergent when soil temperatures average 50°F prevents the germination of weeds like crabgrass, which typically sprout when soil temperatures reach 53°F to 58°F.
The 50°F to 65°F soil temperature range is perfect for seeding or overseeding cool-season lawns. Seeding at this time allows the grass to establish roots before the stress of summer heat arrives. For warm-season lawns, 50°F means they are fully dormant, and lawn care should be minimal to prevent damage to the sleeping turf. Fertilizing should be avoided until the soil warms further, as the grass cannot utilize the nutrients and the fertilizer may instead feed weeds.