Hi David,
I worked with this species in Indiana for many years, making seed collections from wild populations and then including those seeds in restoration seed mixes. Our seed collection dates ranged from early September to mid-October; this was in the NW part of the state. The seeds stay in the capsules relatively well (dehiscence and seed loss was not a concern). Sorry I don’t have information about storage or germination treatments.
Nice plant!
-Stephanie