The following posts from spring 2010 will help kickstart this topic as we head towards spring 2011.
Two photos of Iris cristata 'Sam's Mini', a low growing and floriferous variety found by Sam Norris of Kentucky.
The next photos show the early spring rhizomes when first emerging. The rhizomes run on top of the soil, in fact, they prefer to slowly romp through the top layer of woodland duff or well decomposed bark mulch. In this particular cultivar, the rhizomes amusingly look like they're leaping up and over like spawning salmon as they progress upstream.
Having never harvested seed on Iris cristata, I wanted to experiment with seed-grown plants to see what sort of variability could be expected. I also needed to learn how to harvest the seed; when is the seed ready? Every few days I picked a pod and snapped it in half to test the progress of developing seed inside. Eventually a few pods started to show a small degree of whitening in color, and a few other pods actually dropped off (although remained unopened), surely ready to pick. The succulent green pods of Iris cristata and some Chinese woodland irises are attractive to some sort of insect that gets to the pods before fully ripe; dastardly chipmunks & squirrels munch them too, so harvesting early when the seed is ripe enough makes sense.
In the photo on the left showing the seed pods, on the right notice the lobster-claw like leaf bracts that each hold twin seed pods, the long styles are persistent. Initially when testing seed for readiness, the seeds were nearly clear or translucent... so I waited until they were a semi-translucent to nearly opaque tan or yellow color. Harvesting the seed is as easy as snapping the pods in half, then gently squeezing the seed out. They were sown fairly thick in flats, covered with fine decomposed pine bark mulch, covered with wire mesh to prevent digging by chipmunks and squirrels, and they'll spend the year outside, hopefully to germinate spring 2011.