I had a dahlia last year, that I planted a little deeper then usual, and another that was layed down on its side, more like what you do with a tomato! These where started early, then planted in the garden. I was very happy to see when I dug them out, that not only did they have a few tubers with the mother tuber, as per usual, they had some very NICE additional tubers growing where the leaf nodes had been!!

I don't know if this was a one off or not, but I am going to try it again for all my plants this year...