Diphenyl ethers of the formula ##STR1## where Z.sup.1, Z.sup.2 and Z.sup.3 independently of one another are each hyrogen, halogen, nitro, cyano, carboxyl, alkyl of 1 to 4 carbon atoms, or haloalkyl, alkoxy, haloalkoxy, alkylmercapto, haloalkylmercapto, alkylsulfinyl, haloalkylsulfinyl, alkylsulfonyl or haloalkylsulfonyl where alkyl is in each case of 1 to 4 carbon atoms, Y is hydrogen, halogen, cyano or nitro and Q is --CO--NA--OR.sup.1, where A is hydrogen, alkyl of 1 to 4 carbon atoms, a metal ion or an unsubstituted or substituted ammonium ion and R.sup.1 is carboxyalkyl, alkoxycarbonylalkyl or carbamylalkyl of not more than 10 carbon atoms, herbicides which contain these diphenyl ethers as active ingredients, and methods of controlling undesirable plant growth using these active ingredients.