Critical Soil Temperatures for Grass Growth and Weed Control

Partial list of 4-inch soil temperatures (°F) linked to biological events.

Check your soil temperature here

Cool-Season Grasses: Fescue, Ryegrass

• 90°F – Shoot growth ceases
• 77°F – Root growth ceases
• 70°F – Max temp for consequential root growth
• 70°F – Time to plant in late summer
• 60–75°F – Optimum shoot growth
• 50–65°F – Optimum root growth
• 40°F – Shoot growth ceases
• 33°F – Root growth ceases
• 20°F – Low-temp kill possible if rapid drop 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 bermuda with ryegrass (fall). Time to plant in spring.
• 64°F – Spring root decline triggered; roots brown/die in 1–2 days
• 50°F – Root growth slows below this
• 50°F – Chilling injury/discoloration possible
• 50°F – Dormancy initiation/discoloration
• 25°F – Low-temp kill possible

Weed Control

• 60–65°F – Spurge and goosegrass germination expected → apply pre-emergent
• 53–58°F – Crabgrass germination expected → apply pre-emergent