Jeff from Menomonie, Wi writes
Tenacity Herbicide can be applied any time before the weeds start to germinate. Weeds absorb Tenacity as they emerge from the soil. For the best time to apply pre-emergents in your county we recommend contacting your local cooperative extension office here. Crabgrass seeds will start to germinate when soil temperature are around 55 degrees, so you need to apply it before you have those temperatures for best results.
Answer last updated on: 05/02/2017