Flowering phenology and reproductive allocation are important factors to adapt to the environment. The article studied the flowering phenology and reproductive allocation of Fagopyrum dibotrys. Fagopyrum dibotrys flowered from August to November, mainly in September, centralized flowering contributes to insects pollination and improves reproductive success; Fagopyrum dibotrys flowered 1 to 2 days for a single flower, 85 days for the population. Long-styled capitulum flowered 15 to 26 days, short-styled capitulum flowered 14 to 27 days, the difference is not significant; The flower number of the long-styled single capitulum is 26 to 131, the short-styled capitulum is 36 to 147, the difference is not significant. Flowering dynamic of F. dibotrys's long-styled and short-styled capitulum presented unimodal curve, long-styled and short-styled capitulum both reached maximum 11days after flowering, was 7.30% and 7.20% respectively, and the two floral morphs maintained high synchronization of flowering, contributing to increase the reproductive adaptability. Pistil and stamens length exhibited very significant negative correlation in the same floral morphs, but the total length showed no significant difference, which showed that there is a trade-off relationship; Fagopyrum dibotrys's vegetative organs and reproductive organs biomass existed no significant difference between the long-styled and short-styled, while their floral biomass and plant biomass showed very significant difference. F. cymosum's floral biomass allocation ratio of the long-styled is significantly larger than the short-styled, but the total biomass showed no significant difference, which showed that there is a trade-off relationship in Fagopyrum dibotrys's vegetative growth and sexual reproduction.