Oklahoma’s climate features a sharp transition between hot summers and cold winters, creating a complex environment for turf management. The state utilizes two fundamental types of grass: warm-season varieties, which thrive in heat, and cool-season varieties, which prefer milder weather. Determining when lawn growth ceases depends almost entirely on the grass type. This distinction is paramount because each variety reacts differently to the seasonal drop in temperature, dictating the timing of final lawn maintenance tasks.
The Critical Role of Soil Temperature
The mechanism that triggers the end of the growing season is a reduction in metabolic activity within the grass plant. This slowdown is governed not by air temperature, but by the consistent temperature of the soil surrounding the roots. Soil temperature is a far more stable metric than air temperature, which fluctuates widely. The ground acts as a thermal buffer, holding heat longer than the air above it.
Grass growth continues until the soil cools below a certain point. The universal threshold at which most turfgrass roots and blades cease active growth is approximately 55 degrees Fahrenheit, measured at the root zone depth. Once the soil temperature consistently falls below 55°F, the plant’s metabolism slows significantly, and it enters a protective state to conserve energy for spring.
Dormancy Timing for Warm-Season Grasses
Warm-season turfgrasses, such as Bermuda and Zoysia, are the most common lawn types in Oklahoma and exhibit a definitive cessation of growth. These grasses are genetically programmed to enter a deep, protective dormancy when cold arrives. This process is triggered when the soil temperature consistently stays below the 55°F mark for several consecutive days.
The timing of this hard dormancy varies across Oklahoma due to the state’s significant north-to-south temperature gradient. Homeowners in the Panhandle and northern Oklahoma typically see their lawns stop growing and begin browning in mid-October. This transition shifts later moving south through the state. Lawns in central Oklahoma generally enter dormancy in late October, with southern regions holding onto growth until early November.
Visually, this protective state is unmistakable, as the grass blades lose their green pigmentation and turn a straw-tan color. This dramatic browning does not signify that the grass is dead; the plant has simply retreated its energy into its root system and crowns. The grass is resting, waiting for the soil to warm up again in the spring. Therefore, the average Oklahoma lawn owner can expect to perform their final mowing sometime between mid-October and mid-November.
Growth Slowdown in Cool-Season Varieties
Cool-season grasses, like Tall Fescue and Perennial Ryegrass, behave differently in late fall and early winter compared to warm-season counterparts. Instead of entering a hard dormancy, these varieties experience a growth resurgence when summer heat stress subsides. This autumn growth surge occurs because the cooling air and soil temperatures fall directly into their optimal growing range, stimulating vigorous top and root growth.
As the season progresses toward true winter, the growth of cool-season grass merely slows down considerably rather than stopping completely. They will continue to grow intermittently throughout the winter as long as the soil is not completely frozen. A total halt in growth only occurs during hard, sustained freezes that lock the soil solid.
These grasses retain their green color through the winter, contrasting sharply with dormant warm-season lawns. Homeowners should expect to continue occasional mowing, especially during warm spells. The difference is a gradual slowdown and eventual pause during the deepest cold, rather than the abrupt, definitive dormancy seen in Bermuda or Zoysia.