Roundup is the most effective KILL EVERYTHING herbicide...gotta be careful not to spray on windy days, as it will drift and kill desirable plants. Some plants with "waxy" leaves, like ivy, are hard for roundup to penetrate and one can add a little detergent to it. Follow label instructions! Best time is when stuff is actively growing. To make it most effective, mow weeds if possible and then spray when new growth appears; that way, the plant is taking up all of the spray and making "less is more" work. You might also take a sample of the weed to county extension agent for advice if Roundup doesn't work.