Something that is very close to our hearts is the quality of our products, and our dahlia tubers are no exception. Dahlia tubers are classified into two size groups, Class I and II. For a Dahlia tuber to be classified as size I, the tuber must weigh more than 80 grams, and for size II, it is over 40 grams. Does the size of the tuber matter to the size of the Dahlia plant? Here the answer is both yes and no.