Herbicidal compositions containing silylated chloroacetanilides

A plant growth regulating agent containing as active ingredient an effective amount of a silylated chloroacetanilide of formula I ##STR17## wherein R represents a lower alkyl group having at most 4 carbon atoms, a group --CH.sub.2 --CH.sub.2 --Si(CH.sub.3).sub.3, a group --CH.sub.2 --Si(CH.sub.3).sub.3 or a trimethylsilyl group,

• Z represents a straight or branched alkylene chain having at most 3 carbon atoms,
• R' represents halogen, lower alkyl or alkoxy having at most 3 carbon atoms or trimethylsilyl, and
• n represents the number 0 or 1, together with a suitable carrier.