Abstract: Regulating plant growth with carbamoyl and substituted carbamoyl alkyl trihydrocarbyl phosphonium organic and inorganic salts of the formula ##EQU1## in which R is alkyl of 1-14 carbons, phenyl, tolyl or dimethylamino;R' is hydrogen or lower alkyl;R" and R'" each is hydrogen, alkyl of 1-14 carbon atoms, cycloalkyl of 3-7 carbon atoms, alkenyl of 2-6 carbon atoms, cyanoalkyl having 1-4 carbon atoms in each corresponding alkyl moiety, aralkyl having 1-4 carbon atoms in each corresponding alkyl moiety and optionally substituted with 1-3 chlorine atoms, furfuryl, phenyl, phenyl substituted with 1-3 chloro or methoxy or methylthio or 1-2 alkyl groups having 1-3 carbon atoms; orR" and R'" combined are piperidino, morpholine, 3-aza (3,2,2) bicycloheptyl; andX.sup.- is monovalent anion.Many of the cmpounds are new.