Now is the time to kill any weeds that have popped up in the lawn. The weather needs to be warm and sunny for 3-5 days with no rain or water on the lawn for Weed B Gon to work the best. It comes with a hose-end applicator on the bottle and enough to spray over 2500 sq. ft of lawn area. Do not mow first, but do make sure the lawn is watered well before spraying. And yes, it is safe to use on Floratam St. Augustine. Give it a full 2 weeks to work its magic and by then the grass should be out of winter dormancy and it will be time to fertilize.