There are several of the vendors that list their re-bloomers by "zone", and that's probably a good place to start. But you have to remember a few things,...the USDA zone map tracks the lowest average temperature, and that's certainly important, but it does NOT track the number of frost-free days!, And for re-bloomers, that's pretty important, too.....re-bloom is NOT a certainty , and should be looked at as a "bonus".....The best shot at re-bloom comes from not allowing them the usual summer dormant period, and that means extra water, fertilizer, and care. And that much summer water and food is REAL hard on the "regular" iris in the bed. That said, yes ,in my opinion anyway, re-bloomers are "worth it". You will have the best luck with re-blooming types of SDBs, and IBs, as with their early bloom time, they automatically have a :longer season, in which to re-bloom. I would also suggest you visit Winterberry Gardens website, and get a copy of their catalog. They both are loaded with info on re-bloomers, and their care( as well as lots of "regular" iris tips.)....Arlyn
