Answer: Sports can occur on any portion of the plant or the entire plant. The entire plant sport is found when you grow the tuber the next year. Sports that affect one branch can be “captured” by taking a cutting from the sported branch. How often to dahlia plants sport? I would say if you grow 200 plants of something, you may get s full plant sport every few years. I am leaving out variegation sports that are totally different and need a separate explanation. So how is it a grower has 50 sports? Radiation or chemicals are the answer. Sports are a loss of genetic material caused by damage to the DNA. When you induce sports you probably wipe out many of the good genes required for good growth. Sports are quite often not very vigorous.
