Posted: 16/12/2014 at 19:43
You should grow dahlias, but ask your neighbour, if he has the same soil, and if so, what does he do with them overwinter. Choice is to leave them in, and the cold wet clay may not be great for them, or dig up the tubers after the first frost and store them, replanting in Spring. I am sure he or she will be happy to advise best course for your conditions. I grow loads, but have lightish soil and can leave them in.