Herbicidal control of tall larkspur, Delphinium occidentale Wats. was investigated in the Sawtooth National Forest near Oakley, Idaho. When larkspur was in a prebud stage, 4 and 8 lb/A of the propylene glycol butyl ether esters of 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) gave good control, with significant increases in yield of native grasses. At the bud and flower stages neither herbicide gave satisfactory control at 12 lb/A. Granular silvex at 400 lb/A total product (80 lb/A ae) killed all larkspur with only slight injury to rabbitbrush, sagebrush, and native grasses. A chlorate-borate (25%–75%) mixture gave a complete larkspur kill at 1740 lb/A.