I have this crazy routine for putting my dahlias to bed for the winter. The process takes a whole week. First I make sure that each plant is labeled (kind and color, temporarily tagged on the stem with a twisty tie) before the last frost hits, because once the leaves turn black and the flowers die off I'd never know my Emory Pauls from my Chloe Janaes. I wait until the frost so that the leaves have all the time they can to send energy down to the tubers, which will actually grow eyes over the winter (the way a potato tuber does). When the frost hits, that's my cue to dig up my dahlia plants. I carefully dig them out of the ground, hose the dirt from the tubers, and line them up on the grass by kind with their specific labels all ready to attach. Then I cut off their lush green tops. Off with their heads!
Here are the labels, all ready to attach to the bags that they each will go into. You can still see some of the names stamped onto the dahlia tubers from the sellers, and all the new tuber growth. Some experts say to discard the 'mother tuber', and break apart your tubers at this point, but I always overwinter the tubers as they are, and divide them in the spring. I can see where they eyes have sprouted over the winter.
Then I dry the dahlia tubers out for a week or so, preferably with the tubers upside down so any moisture from the cut stem will drain out. Then off they go into a ventilated box for the winter, where they stay on my porch. Where you store your dahlia tubers must have a constant temperature of between 32° and 50°, and the moisture should not be too dry or too damp. It's a little tricky, but worth the effort. I check on the dahlias every month or so to make sure there is no fungus on the tubers. I am excited for next spring, when I can put these chickens back into the ground.