Pyrandione, thiopyrandione and cyclohexanetrione compounds having herbicidal properties have been found. Accordingly, the invention relates to a compound of formula I wherein Y is O, C=O, S(O) m or S(O) n NR 5 ； provided that when Y is C=O, R 3 and R 4 are different from H when either R 1 or R 2 is H, and R 1 and R 2 are different from H when either R 3 or R 4 is H； m is 0 or 1 or 2 and n is 0 or 1； and Het is an optionally substituted monocyclic or bicyclic heteroaromatic ring (heteroaryl), as defined in the description； and G is hydrogen, an alkali metal, alkaline earth metal, sulfonium, ammonium or a latentiating group.
