Eupatorium perfoliatum L. (N-Am.) – A very rare escape from cultivation. Known since 2007 from the margins of a small pond in a private garden in Brugge (a single individual, probably unintentionally introduced with other ornamental plants).
Eupatorium perfoliatum is a very distinctive species within the genus, the only one with perfoliate leaves.
According to Whitehouse (2007) it can be fairly invasive.
Selected literature:
Whitehouse C. (2007) Eupatorium: Joe Pye weeds and their ornamental relatives. The Plantsman N.S. 6(4): 242-247.
Taxonomic name: