Eupatorium or Eutrochium?

This is a colony of Joe Pye Weed.   It's tall - about 8' tall.    The flowers are varying shades of mauve.

This one is just ready to open but gives you a good idea of the color.  When fully open it looks quite fuzzy and the bees and butterflies and hummingbirds are all over it. 

This is one of many Eupatorium varieties we have here - tall ones, short ones, white, pink, blue...we have a bunch.   Or it's a type of Eutrochium - hard to tell.   I've seen almost identical photos in descriptions of both.

The leaves are opposite and 5 or 6 of them surround the stem.   Sometimes the stems are spotted and the flower heads a bit flatter [Spotted Joe Pye Weed.]    It likes moist areas around creeks and bogs.   We have a lot of it along the creeks.