The Louisiana Native Plant Society is a great place to start. Dr. Charles Allen is heavily involved with that group and is also a great resource. He leads expeditions to see rare habitats. I got to go last spring and we saw quite a few Cyp. kentuckiense, Calopogon oklahomense, a few Pagonia ophioglossoides. We were hoping to find Isotria verticellata (spelling?) but it eluded us.
Thank you for all the helpful responses!
Kip, where did you find this list? I searched the web for days, and only found four or five natives.
I will definitely look into Mr. Brown's book and the LA Native Plant Society.