You have to remember that rebloom isn't really "guaranteed", for any iris..anywhere. It can be "highly likely", under most average growing conditions, for some of the most reliable rebloomers, but still, not "guaranteed'. I grow a lot of Re irises, but only "know" what works in my zone 5, Northern Illinois, garden, so, what works in your climate is new territory, for me.
I feel that, for the best rebloom chance, the plant can'r be allowed to go dormant during the growing season....irises want to take a "rest period" after spring bloom, and that is when we usually are doing the digging, dividing, planting, in our beds, so everything is ready to "take off" when that dormant period is over. In a "normal" year, that means fertilizing right after spring bloom is over, and maintaining the moisture level in the beds (never letting the soil dry out deeper than , maybe 2 inches deep....the rhizomes set in the top inch, or so of soil....which can...and should, be dry, but the roots are all in the 3"-8" depth range), controlling weeds, and leaf spot, to keep the plants growing at "maximum efficiency ". That can be hard, in some areas , in some years. Also, the plants chosen should be ones that are known to do well in your area...some irises take a longer time to mature a rhizome, so, in my "short season", there just won't be enough "year" for them to ever rebloom. Check out the "Reblooming Iris Society" for some information, and some tips.
http://www.rebloomingiris.com/
