Joe Pye Weed

Eupatorium fistulosum (Eupatoriadelphus fistulosus) Joe pye weed

Close up of the individual flowers (florets) of Eupatorium fistulosum. If you look closely (these photos can be magnified), you can see there are around 4-7 florets per involucre (flowerhead). If it were E. maculatum it would have 10-16. This is an easily ascertainable characteristic. Pluck an individual involucre (consult botany books on the Asteraceae to learn terms) and roll it in your fingers gently and you should be able to count the individual flowers.