Four clones of sweet potato were planted monthly in 1984, and 11 morphological and growth characteristics were measured. Clones differed with respect to all characteristics, and significant differences were found among months in all but one characteristic. The 11 characteristics could be classified as modal, bimodal, irregular or complex with respect to monthly distribution. Several of the characteristics regressed on months by linear, quadratic or cubic regression. Others were not clearly related and differences are believed to be caused by cultural factors that may have varied. Four external variables affecting sweet potatoes, (day length, rainfall, temperature and solar radiation) could have accounted for many of the observed differences among months.