Herbicidal compositions containing a bisphosphonic acid compound of the formula ##STR1## wherein n is 0, 1, 2, 3, 4, 5 or 6, or an agrochemically acceptable salt or hydrolyzable ester thereof and methods of controlling undesirable plant growth using these bisphosphonic acid containing compositions. The herbicidal compositions exhibit desirable efficacy when applied to plants post-emergence, but exhibit little significant activity when applied to plants pre-emergence. Novel aza-bisphosphonic acid compounds are also disclosed.