Novel cyclohexanedionecarboxylic acid derivatives have herbicidal and plant growth regulating properties. The cyclohexanedionecarboxylic acid derivatives have the formula I ##STR1## wherein A is an --OR.sub.2 or --NR.sub.3 R.sub.4 radical,R is C.sub.1 -C.sub.6 alkyl or C.sub.3 -C.sub.6 cycloaklyl, each unsubstituted or substituted by halogen, C.sub.1 -C.sub.6 alkoxy or C.sub.2 -C.sub.4 alkylthio,R.sub.1 is C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 haloalkyl, C.sub.3 -C.sub.6 -alkenyl, C.sub.3 -C.sub.6 haloalkenyl or C.sub.3 -C.sub.6 -alkynyl,R.sub.2, R.sub.3 and R.sub.4 are each independently hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 haloalkyl, C.sub.2 -C.sub.10 alkoxyalkyl, C.sub.2 -C.sub.10 alkylthioalkyl; C.sub.3 -C.sub.6 alkenyl which is unsubstituted or substituted by halogen, C.sub.1 -C.sub.4 alkoxy or C.sub.1 -C.sub.4 alkylthio; C.sub.3 -C.sub.6 alkynyl; phenyl or C.sub.1 -C.sub.6 aralkyl, wherein the phenyl nucleus is unsubstituted or substituted by halogen; C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 haloalkyl, nitro or cyano; one of R.sub.3 and R.sub.4 is methoxy orR.sub.3 and R.sub.4, together with the nitrogen atom to which they are attached, form a 5- or 6-membered heterocyclic ring system which may contain an additional oxygen or sulfur atom in the ringor a metal or ammonium salt thereof.