Not all weeds can be controlled by herbicides. Of the three types of weeds we are seeing in Northeast Florida, the broadleaf (i.e. dollar weed) and sedge can be controlled with herbicides. Grassy weeds (i.e. crabgrass) simply needs to be removed by hand. There is no selective herbicide on the market today that will kill grassy weeds without killing the grass itself. If you see that weeds have started flowering, pull them up immediately or they will blow seeds across your lawn, creating more of a problem.