The question of whether grass continues to grow after a frost depends heavily on the grass type and the severity of the cold event. Frost occurs when air temperature drops to or below 32°F (0°C), causing water vapor to freeze on grass blades. This environmental cue triggers biological mechanisms that either slow growth significantly or induce a deep, protective dormancy. Understanding these differing reactions is key to knowing what to expect from your lawn after a cold snap.
How Grass Species React to Freezing Temperatures
Turfgrasses are categorized into two groups based on the temperature ranges where their growth is most active: cool-season and warm-season varieties. This classification determines their immediate reaction to freezing temperatures.
Cool-season grasses, such as Kentucky Bluegrass and Tall Fescue, thrive in temperatures between 60°F and 75°F. These grasses are generally more tolerant of cold and can maintain slow growth during mild frosts or brief thaws. Their growth stops entirely when air temperatures drop consistently below 32°F or soil temperatures fall below approximately 40°F.
In contrast, warm-season grasses, including Bermuda and Zoysia, prefer much warmer conditions, with optimal growth occurring between 80°F and 95°F. These grasses enter a state of deep dormancy almost immediately upon the first hard frost. The grass blades lose their chlorophyll, turning a distinct brown or tan color, and cease all visible growth until sustained warm weather returns.
Dormancy Versus Damage: The Cellular Response to Frost
The grass’s survival response to cold is a distinction between controlled dormancy and physical cellular damage. Dormancy is a self-preserving strategy where the plant halts growth and conserves energy in its protected crown, the base of the plant near the soil line. Even if the blades turn brown, the crown remains alive, protected by the insulating soil and its natural defenses.
Freeze damage occurs when the temperature drop is too sudden or severe, causing ice crystals to form within the plant tissues. If ice crystals form inside the cell (intracellular freezing), they rupture the delicate cell membranes, leading to immediate cell death. More commonly, ice forms in the spaces between cells (extracellular freezing), which draws water out of the cells.
This process causes the cell to become severely dehydrated, or desiccated, resulting in membrane damage and the visible browning of the grass blades. A light frost typically only damages the exposed tips, but a severe or prolonged freeze can threaten the crown itself. Walking on frosted grass compounds this damage, as the frozen, brittle cell walls shatter easily under pressure, leaving behind distinct brown footprints that may take weeks to heal.
When and How Growth Resumes
The resumption of growth is signaled by a sustained increase in soil temperature, not a single warm day. The soil acts as a thermal buffer, and its temperature dictates the activity of the grass’s root system and crown. For most dormant grasses, consistent growth will not resume until the soil temperature stabilizes above 50°F.
Once this temperature threshold is met, the grass crown begins to push out new green shoots, reversing the dormancy. The speed of recovery depends on the grass type and the extent of any prior freeze damage. Post-frost care involves avoiding heavy foot traffic on frozen blades to prevent mechanical damage to the brittle tissue. Homeowners should wait until the ground has completely thawed and the grass is actively growing before applying fertilizers or undertaking heavy maintenance.