Back when I was a younger ( read "inexperienced") gardener, I kept trying them here and they behaved mostly like annuals. They do not tolerate our hot dry summers here at all. So, I think the answer is, it depends entirely on your climate. I grow spiky perennials now that DO tolerate this climate. Back in 2008, I've never been so shocked as when I was on a National Daylily tour in Houston, TX, and one of the garden had blue delphiniums! They HAVE to be grown as annuals in that hot climate. I can't imagine them surviving a summer in Houston!
