Do Happy Single Dahlia's need to be brought in in the winter?

It depends on where you live. According to The Garden Helper:





"Dahlias are summer blooming tubers which are generally only hardy in USDA zones 7-11. In the majority of the country, they must be planted each spring and then cut back and dug each fall after the first killing frost."





Zone 7 is Oklahoma and it goes south from there. So, if you are down south, you can leave them in; otherwise, lift them!





Good luck and check the link for more information.