A True Butterfly Magnet. There are few flowers that merit the term "butterfly magnet" but the Joe Pye Weed is one of them. This picture shows three species of butterflies (including a small copper) nectaring on the inflorescence. The Joe Pye weed is closely related to our Hemp Agrimony. It can reach up to 7' high although the one we grow is a dwarf cultivar more appropriate for smaller gardens. This plant has a fairly short flowering season in September.