By Lynnef
Cambridgeshire,
United Kingdom 
hello, i have two very old, very established dahlia shrubs, they're both still flowering well and look lovely, however, they have now outgrown the space and take up so much room (I've never lifted them). After this years flowering has finished, can i lift the tubers and split them or will this damage them? I'd like to spread them about, thanks, Lynne.
14 Aug, 2016
Answers
Just remember that they grow from the old stalks not the tubers so removing and planting the tubers is a waste of time.
14 Aug, 2016
Yes, each tuber needs a piece of stalk with a viable bud to grow. It's often safer to plant groups of three or four tubers sharing a segment of stalk, than to reduce it to singletons.
14 Aug, 2016
Thank you, that's very useful, Lynne.
14 Aug, 2016
I have in the past cut vertically down a stalk to created divisions, but you have to be very careful in doing it. Those were the days when I grew Dahlias. Here they are a waste of time. We have never managed to get them to survive our early and late frosts.
14 Aug, 2016
Previous question
Yes, when the flowering season ends and they go dormant, you may dig them & split them. That's when it's normally done. Usually right after the first hard frost when the leaves turn black.
14 Aug, 2016