Jim for ground cover and plants that Horsetail or other weeds are growing up in. We use different size pvc pipe and fit it around the weed(what ever it is) then use sprayer and spray in Pvc pipe. Leave pipe there untill weed(what ever it is) is dead. It is a pain but better than redoing the entire landscapeing at your cost. Most customers are not willing to pay for redo when they are paying you monthly to make sure the beds are clean of weeds.
What ever I do I must do it right!