Carolyn asked about growing I. japonica in New York.
There are some good articles on crested iris in the Fall 1995 (No. 55)
issue of SIGNA, the species iris group newsletter. In one, Darrell Probst
in Mass. says that most of the crested iris are tender for him.
He grows them in pots which he brings into the house in the winter.
He uses a mix of 2 parts of Pro-mix, one part bark chips and one part
granite grit (1/8 to 1/4 in). The granite keeps the mix loose and gives
it the weight necessary for the pot to support the bloom stalks.
Rodney in Texas where I just potted my sole remaining fan of I. japonica
in a last ditch effort to save it from the heat and drought.