I usually think of "repeat" bloom as that of the *beardless* iris, SIB's, for example. The bearded iris that bloom "again", several weeks after the first stalks appear, seem to always be the ones that are registered as E-M-L (early, midseason, and late), and are all blooming on increases that started growth the year before. The "reblooming"(Re) bearded ones, make their late summer, or fall, for the most part, bloom on "new" increases, that have started growth in the early spring. That said , there are some bearded iris that are "E-M-L" AND "Re", and can, in the right climate and under the right cultural conditions, be "almost" everblooming. The "confused bloom" can, and does happen, and not only on newly planted rhizomes, though that is usually when you see it. When temperature and moisture conditions are "just right", that rhizome thinks it's spring.....it's had it's dormant period, and if there is a "eye" (not sure of the correct terminology, but the spot on the rhizome that produces the stalk), and if the rhizome has had a long enough period to mature , it blooms.
