Greetings'

I just recieved one of my dahlia's as a big clump. I just went ahead and potted mine up. I'm going to divide it up this fall.

Moonlite

I would divide them now. But I would prefer multiple plants than a plant with multiple stems. If you are concerned about burying them right after dividing, just nestle them halfway into the soil of the pot to start with, and then bury them deeper as they grow.

Last year I had some tubers that were to large to fit into the pots I was using. I just cut off the end of the tuber (about 1/3 on some of them) and it didnt seem to slow them down at all.