Back in my flower show days (the late 1970's), I discovered that many cut flower stems could be rooted after the show was over, with dahlias being one of the most successful. You will need to be sure that there is one vegetative bud on the shoot to be rooted. Since we had our shows in October, I kept them indoors over the first winter, so they could develop a tuber after rooting. I think there are lots of propagation opportunities missed when flower show specimens are discarded. And of course when that fabled black or blue sport Dahlia occurs as a side shoot it will be the only way to do it. Almost anything will root with care but a side shoot helps considerably the next stage to that fortune you dream of. Brian