Round-up looks like the strong item for this.....doing it by hand and getting all the roots out could be hard to do.......so 2 options at hand.....If you choose round-up follow the directions carefully wearing the proper attire & gear...........keep children & pets away from this area.....some grass my die doing this so try to limit it right at the root............bag & trash the dead pieces and I would put the bagger on when you cut the grass to keep any flowers from speading any place else in your yard.