I stopped trying to grow exotic rare things when confronted with the reality that I frequently repeatedly kill locally native common things. Iris cristata & Iris verna are native within miles of my home... and yet my garden has been a graveyard to them. "Abandon hope, all ye cristata & verna who enter here." I do grow some super cool rare/endangered species like Iliamna remota, Boltonia decurrens, Silphium wasiotense, Echinacea tennesseensis, Silphium brachiatum, but they're not in the same league as what all y'all are talking about. (Silphium wasiotense is so elusive you can't even find a picture of it on Google.) And they're inclined to thrive in my garden anyway, being regionally native. Dennis in Cincinnati (who doesn't even have an import permit anymore)