Joe Pye weed is a robust, upright perennial with hollow purple stems accented by huge, rounded, tight clusters of pink or purplish-mauve flowers. It is an important pollen and nectar plant and attracts butterflies (particularly the swallowtail butterfly) and other pollinators by the dozens. Its height makes it an excellent background plant in border perennial beds, but is also majestic standing alone. Flower color is darker in cooler weather.