I have been taking a crash course this year in irises, trying to determine why I lost so many in the last 15 yrs. So I picked up a book on irises from 1965(all I could find at Amazon) that had a lot of important facts about growing irises. Back in the 60's they used 2 different species in the parentage of TB's. One was used mostly in the midwest and required more moisture to do well. The other was used in Cal. and so their offspring do better in dry sunny areas. There has been so much mixing since then that I don't know if it still holds true but I know I never had any problems with iris here in Tx until I bought some from Missouri. I have never even thought about watering Texas grown iris but know now that I may have to when ordering some of the newer irises. Also people don't realize what diseases or pests may be affecting their plants until it is too late. Here I've recently found grubs from June bugs and pocket moles that tear thru roots. Some even have to deal with other diseases such as 'scorch' which may be caused by mites and/or severe weather changes.
I recently talked with Mrs. Horton from Horton Iris and she has to deal with big gophers and uses a systemic for ground insects, as well as a pre-emergent herbicide for weeds, and fertilizer twice a year. I'm sure some small growers have great organic methods for growing iris, but it's just tough to do on larger plots.
So really we don't have much choice if we want some of the newer varieties, we just have to keep an eye on the plants year round, treat them when necessary, keep up the fertility and plan on using extra water when droughts hit. Also it's tough, but we still have to dig them up and replant them every 3-5 yrs or so to keep them blooming.
Maybe some day we'll have a data base for the more vigorous plants for those of us who still just like to plant them and watch them bloom. LOL
Getting back on topic, I just read an article by Don Spoon and he says that there is no real difference in cold hardiness in the recent introductions. I'm assuming the irises released in the last 20 yrs or so. Probably because of so much cross breeding.
