Welcome to All Things Plants,
@Kinsella217 !
That's really an interesting question, I wish I knew the answer for you... I will say that one spring my brother-in-law dropped off a bag of dahlia roots that had sprouts at least a foot long, which had been stored in his basement for 2 winters without ever being planted -- and they still grew well for me! So, I'd say dahlias are pretty tough and you have a very good chance of success with your "forgotten" roots!
