new genus Eupatoriadelphus in 1970. This was widely accepted, and Joe Pye weeds began to be referred to as such.

In 1987, Robinson and King reincluded the genus Eupatoriadelphus in Eupatorium, while recognizing this former genus as being the same group of plants as Rafinesque's Eutrochium. This decision was also widely accepted.

Based on chloroplast DNA analysis published by Edward E, Schilling et al. in 1999, the Joe Pye weeds were again separated into their own genus, Eutrochium, as Eutrochium is the senior synonym

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