By Trish Svoboda

Cynthia Domenghini, a horticulture expert from Kansas State University, highlights the significance of soil temperature for home gardeners. She notes that soil temperature profoundly impacts the germination of various garden crops.

According to Domenghini, peas can sprout in soil as cold as 40 degrees Fahrenheit, while lettuce can germinate in temperatures as low as 35 F. However, warm-season vegetables like tomatoes and corn require soil temperatures of at least 55 F for optimal growth. Peppers, cucumbers, and melons need even warmer soil conditions.

To monitor soil temperature, Domenghini suggests utilizing resources like the Kansas Mesonet or taking measurements with a soil thermometer, probing at least 2.5 inches deep during late morning. She advises gardeners to calculate the average soil temperature over five days to determine the best planting time, while also remaining vigilant for late-season frosts and freezes in the forecast.

Domenghini and her colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens. The newsletter is available to view online or can be delivered by email each week.