All irises have pods with three valves that open and spread when seeds are mature and pods are dry. Open pods toss seeds a few feet, shaking seeds out in the wind and opening a bit more from day to day. Iris pods often open at inconvenient times, usually on hot sunny days when I'm away from home. This was a frustrating reality for me when I started crossing plants and saving seeds, because I'm often hiking in mid summer, away in the hills when those pods pop open.
I. douglasiana has green pods with three valves. Bag and save upright pods, not the sprawling stems. You will find the mature pods more easily later if they are upright.
Iris douglasiana has the longest ripening period. Pods may take nine weeks to fully mature.
Mesh bag on green pod––unobtrusive, discrete, and could be easily overlooked in a few weeks when the seeds are ripe.