Description: A Eupatorium purpureum with the separated individual flowers of one involucre (flowerhead) on the left and an intact involucre on the right. In this photo you can see the individual flowers more clearly. One of the main distinctions between Eupatorium purpureum (along with E. fistulosum) compared to E. maculatum is the number of flowers per involucre. In E. purpureum and (E. fistulosum) there are approximately 4-7 florets while E. maculatum has about 10-16. This is not an obscure reference, if you unroll the involucre in you hand, it is pretty easy to count the florets. For more differences, see other Eupatorium photos.