There is currently a good deal of interest in the "biennial" life history. This stems from the fact that theoretical analysis of the selective advantage of alternate life histories predicts that biennials should seldom be favored relative to annual or perennial alternatives (Hart, 1977). However biennials often appear highly successful in terms of abundance, being both common and widespread, even though they constitute only a small proportion of any flora. This paper describes the effects of latitude on the relationship between rosette diameter at the end of one growing season and a plant's fate in the next (death, continued vegetative growth, or flowering) for populations of the "biennial" species Verbascum thapsus.
Reinartz, J.A. 1980. Latitudinal variation in the relationship between rosette diameter and fate in common mullein (Verbascum thapsus L.). Field Station Bulletin 13(2): 12-18.