Lettuce Soil Temperature Guide
A cool-season crop that germinates in cold soil and tolerates light frost.
| Minimum germination temp | 40°F (4.4°C) |
|---|---|
| Optimal germination temp | 75°F (23.9°C) |
| Maximum germination temp | 85°F (29.4°C) |
| Danger zone | Below 40°F — seeds rot or fail to sprout |
Is your soil warm enough for Lettuce?
Minimum needed: 40°F
Why soil temperature matters for lettuce
Soil temperature directly controls enzyme activity inside lettuce seeds. Below 40°F (4.4°C), germination slows dramatically or fails entirely—seeds may rot before they sprout.
When to plant lettuce in your region
Sow lettuce outdoors when your soil consistently reads 40°F (4.4°C) at 4-inch depth. For the fastest germination, wait until it reaches 75°F (23.9°C).
Signs your soil is ready
The easiest method is to track your local soil temperature forecast until it's predicted to stay above 40°F for the next 7 days—sign up for notifications when it's time to plant lettuce. For more precise readings in raised beds, pots, or different spots in the garden, push a soil thermometer 4 inches deep in the early morning.