Joe Pye Weed Roots Atropurpureum is a stately native perennial that produces massive clusters of deep mauve-purple flowers atop dark, wine-colored stems that can reach five to seven feet tall! Blooming in late summer, Atropurpureum is a favorite of butterflies, especially monarchs, as it provides valuable late-season nectar. We love this variety especially because it adds both height and ecological richness to the pollinator-friendly landscape.