A synergistic herbicidal mixture comprising A) at least one 3-heterocyclyl-substituted benzoly derivative of the formula I in which the variables have the following meanings: R1, R3 are halogen, alkyl, haloalkyl, alkoxy, haloalkoxy, alkylthio, alkylsulfinyl or alkylsulfonyl; R2 is a optionally substituted heterocyclic radical selected from the group: isoxazol-3-yl, isoxazol-4-yl, isoxazol-5-yl, 4,5-dihydroisoxazol-3-yl, 4,5-dihydroisoxazol-4-yl and 4,5-dihydroisoxazol-5-yl; R4 is hydrogen, halogen or alkyl; R5 is alkyl, R6 is hydrogen or alkyl; or one of its environmentally compatible salts; B) nicosulfuron (II) or one of its environmentally compatible salts; and C) at least one herbicidal compound from the group triazines or one of their environmentally compatible salts, in a synergistically effective amount. Compositions comprising these mixtures, processes for the preparation of these compositions, and their use for controlling undesirable plants.