Crabgrass pre-emergent soil temperature guide

Apply crabgrass pre-emergent before crabgrass germinates. University extension guidance commonly uses about 55°F soil temperature as the key threshold. Penn State notes crabgrass can germinate when temperatures in the upper inch of soil reach approximately 55 to 58°F at daybreak for 4 to 5 days, and University of Minnesota Extension says pre-emergent herbicides should be applied before soil temperatures have reached approximately 55°F.

• Open the Soil Temperature Tracker and check your current 2-inch reading and 7-day trend.
• If your soil is approaching the low-to-mid 50s, plan the application and water it in according to the product label.
• Use the GDD Calculator as a second signal for spring heat accumulation, especially when the weather swings quickly.

Pre-emergent products vary by active ingredient, grass type, application rate, watering requirement, overseeding restriction, and residual length. Use the soil-temperature signal to choose the window, but use the label to decide whether the product is safe for your turf and situation.