Everything I've been reading on app's has always said to apply while the weeds are actively growing, or as I understood it---before mowing. This gives more leaf volume for the herbicide to absorb into the plant. At least that's how I read it. Had a lady lean over her fence the other day and wanted weed control price and a mowing price. I gave her the name and number of our local company and told her she needed to call them first so they could do the application, then I would come back and mow it. She called me yesterday and said that the Chemical company wants me to mow it first so they can spray it! I'm confused They also (this is related to another thread concerning pricing) quoted her a price of $33.00 for the yard. It measures out at around 20,000 sq ft.