Head from Chucktown Sc writes
Southern Ag Lawn Weed Killer with Trimec is a post-emergent product that can be applied at any time weeds are actively growing. For best results, apply when broadleaf weeds are young and tender. Hi-Yield Crabgrass Weed Control is a pre-emergent. It is meant to prevent crabgrass from germinating, so it has to be applied before it starts to germinate. This will vary from region to region. For the best timing to apply a pre-emergent in your specific location, we recommend contacting your local cooperative extension office.
Answer last updated on: 10/29/2018
