The University of Massachusetts Extension recommends the use of sethoxydim for the safe control of grasses in flowers. The chemical is sold under different trade names.
Products containing sethoxydim provide selective postemergence control of both perennial and annual weeds in flowers, fruits and broadleaved vegetables. The herbicides may also be used indoors and is sold in the form of an emulsifiable concentrate.
Apply sethoxydim to grasses when plants are in the active stage of growth and before they have reached maximum size. The herbicide is safe for a number of flowers, including chrysanthemum, dahlia, gladiolus, iris, tagetes, aster, zinnia, salvia, coleus and lavendula.