There are two native perennials that are closely related, but look quite a bit different. The first of these is called late-flowering boneset (Eupatorium serotinum). It is a rather ugly plant, but we received several from a relative and were told that "butterflies love them." We were just starting our gardens and were thankful for anything that remained alive more than a few days. The boneset did very well, producing gray, hairy looking blossoms, which attract mostly flies and bugs, and surviving the remodeling of several gardens around them. They grow to about several feet and are very popular with many insects, some of which completely kill a few of the stems each year. The leaves are so riddled with holes by the end of the summer that it looks like that's their natural condition. If you don't look too closely, they are lacy in appearance. They have propagated by seed into several areas of the yard and there is a certain strange attractiveness in the delicate form of the dull, dirty looking flowers.
Purple mist flower (Eupatorium greggi) is a rather invasive, low growing plant. It has lovely, deeply notched bright green leaves and pretty, lavender flowers. Although it spreads quickly, it is easy to pull up when it gets out of bounds. The flowers are relished by butterflies, especially queens, which are sometimes present in sizable numbers, and occasionally small caterpillars attack the blossoms. Other names for this plant are blue boneset, hardy ageratum, and wild ageratum. There are several other plants with very similar flowers, but they are different species and some have different growing habits.