First, this is considered an invasive species in several states, mine included. I don't know how many more may have been added in recent years but "Iris pseudacorus is reported as invasive in Connecticut, Delaware, Maryland, New Hampshire, North Carolina, Oregon, Tennessee, Virginia, Vermont, Washington, Wisconsin, and West Virginia (Forest Health Staff 2006)."

You would want to look at your own states invasive species lists and see if there are restrictions - and truthfully, there are many more pretty yellow iris that are not invasive that you could enjoy growing.

As for the seed pod, it would be ripe when it begins to brown and split open at its 'seam'. This iris, like many, does best with a warm moist, cold moist, cool moist (and in that order) sequence. Part of the problem with them is they self sow as one means of increasing, seeds dropping in late summer to Fall to germinate the following spring. That means sow in Fall, or sow at 68F for 4 weeks, move to 39F for 6 weeks, then move to approx. 55F for germination They should flower in their third year.