I think the Darwins are supposed to be the longest lived. The ones that absolutely come back every year are the common yellow and red. Also Daydream, Spring Green, Renown, and a red/orange/yellow combo with fringe - forgot the name. I have a couple new ones that I planted last year, American Dream and Formosa, a gorgeous yellow and green. I dug up any that were in my way and left the others over summer. I used to dig them up every year, but often the ones I left were the ones that came back, as too much human error happens with the dug ones. I haven't had much luck keeping the white or cream ones going, for some reason.
