Dahlia imperialis is semi hardy and from our own experience will stand a normal winter left outside if mulched, regrowing from the root stock again in late spring the following year. In the UK probably around 3.6 metres is the best you may see in a season but in it’s natural habitat 10 metres is quite normal for 9 months growth! It does flower with pretty single pink flowers in around November if no significant frosts by then. Has to be seen to be believed with huge 8cm diameter stems and massive leaves.
