|I bought a bag of dahlia bulbs. The packaging says|
|Both tubers and bulbs are underground storage units for aboveground plants. Dahlias can be grown from seeds but as the plants mature the roots become swollen and develop into tubers. You can plant the offsets (little bulb-like growths). They will grow into plants but because they do not yet have a lot of energy stored, the plants probably won't flower the first year.
Hope this answers your question!