"Can someone tell me why an iris would bloom beautifully one year and then not at all the next?
Why do some iris I purchase bloom the very next season, and some have been in the ground for 3 years without blooming?"
lot's of good info has already been given...but don't overlook the obvious! For "good' , consistent bloom, irises need plenty of sun exposure, and correct soil fertility and ph. Irises that "tend" to need lots of division, in order to bloom (Immortality is a prime example) are "telling you" that they may have used up the "food" they need! As was stated, iris cultivars are all "individuals"....some make way more growth, in way less time...than others, and "more", or "faster" take more nutrients. And NOT just the usual "N, P, K" that is in most fertilizers ! There are lots of "micro nutrients" involved, as well. That's why "new dirt" (or compost)makes such a difference , when they are moved / reset.
I read , once, that an iris rhizome has to "grow" a certain number of leaves, before it will make a bloom stalk (Being old...I don't remember WHERE I read it
, and I'm not sure HOW many leaves ....I think it was 11), so they need to make pretty, rapid growth to do that.
