I grow dahlia as Jim grows hymenocallis and ismene. The difference is that I leave the soil on. I don't water, but they are plump in the spring and usually sprouting when I plant them out in May. I have them (the tubers, one dahlia) in a cardboard box in a cold room (down to 50F in winter). By the way, I grow lots of onions, and they are still viable in July the year after. I put them into a cardboard box and they are in the same cold room. Of course the room has been extremely hot in late summer and they dry well. Carol