The following is a partial list of soil temperatures (°F) at the 4-inch depth that are associated with certain biological events.
Cool Season Grasses: Fescue, Ryegrass
90°F Shoot growth ceases.
77°F Root growth ceases.
70°F Maximum temperature for root growth of any consequence.
70°F Time to plant grasses in late summer.
60-75°F Optimum temperature for shoot growth.
50-65°F Optimum temperature for root growth.
40°F Shoot growth ceases.
33°F Root growth ceases.
20°F Low temperature kill possible if temperature subsequently drops rapidly below 20°F
Warm Season Grasses: Bermuda, Zoysia, Centipede, St. Augustine
120°F Shoot growth ceases.
110°F Root growth ceases.
80-90°F Optimum shoot growth.
75-85°F Optimum root growth.
74°F Optimum time to overseed bermudagrass with ryegrass in the fall. Time to plant grasses in the spring.
64°F Expected spring root decline is triggered and roots turn brown and die within 1 or 2 days.
50°F Root growth begins to slow below this temperature.
50°F Chilling injury resulting in discoloration is possible.
50°F Initiation of dormancy occurs resulting in discoloration.
25°F Low temperature kill possible.
60-65°F Germination of spurge and goosegrass is expected, therefore, apply preemergent material when soil temperatures approach this level.
53-58°F Germination of crabgrass is expected, therefore, apply preemegent material when soil temperatures approach this level.