That is a threadleaf ironwood (V. lettermanni); these are not the giants. The cultivars of V. lettermanni all stay around that same height. I've got a couple of "Iron Butterfly" that are quite nice.

I've got the big guns, too -- New York ironweed (V. noveboracencis), and some V. fasiculata. Totally different foliage. If you've got the room and like big, beefy plants they're well worth the price of admission.

Thanks @porkchop_z5b_MI for the correction.

And as mentioned, no room in this garden for the "giants".

Well, I will say the "Iron Butterfly" is a well-behaved, attractive plant, and the fine-textured foliage is a nice contract to bolder-leaved plants. Nothing seems to bother it, and it's not floppy in the least. So the "Prairie Princess" is probably worth a try, or try to find an "Iron Butterfly" locally.

I have 3 'Iron Butterfly' and they do split open in summer. I've recently read that they can be given the Chelsea chop in May or early June to prevent this so that's the plan for next season.

BYW, they set prodigious seed--I expect all the cultivars to the same-- which do not come true to the cultivar, so I shear the tops before we go into winter and leave the rest of the plant for the insects to overwinter in.

Thank you for this rouge. I am very fond of Vernonia and have been looking forward to getting V. lettermannii, either the species or a named variety. I have V. crinita Mammuth and it is a wonderful large variety. Apart from liking the plant itself butterflies flock to it. I will check out the others you mentioned porkchop.