WHEN DO I START PRE-EMERGENT? This question has been rolling in, so I think it is time for a rule of thumb. Here in our region of Kentucky, if you go with March 15 for Summer weeds and September 15 for Winter weeds...You will probably do well. That said if you want to be spot on with your application, you will need a
Rapitest Soil Thermometer. Crabgrass seed germinate when spring soil temperatures above 50 degrees F are sustained. "Weed scientists use 52 degrees F. at one-half inch deep as the trigger point for their application of pre-emergence herbicide".
