Variation in flowering phenology of Cassia fistula Linn. population in Ota, Ogun state, Nigeria

Abstract

Flowering phenology in the population of Cassia fistula Linn. at Ota, Ogun State, Nigeria was investigated for three years to determine if there was variation in the phenology and the patterns were compared with some environmental factors to determine if there was any correlation. The number of plants flowering each month was monitored for three years. Data for mean monthly maximum and minimum  temperatures, mean monthly rainfall and number of days with rain per month were obtained from Meteorological Institute, Oshodi, Lagos- Nigeria. In each year, there was synchronous flowering showing early and late flowering plants but the start and end of flowering vary between years. The peak months of flowering vary from year to year so also the period of flowering. Statistical analysis showed significant difference in flowering pattern between two of the years and from month to month. All these show clear variation in the flowering phenology of the species. 

Commencement of flowering was correlated with the rainfall and temperature in July and August while the end was correlated with the amount of rainfall and number of rainy days. With the overlap of flowering between the years, flowering is continuous in contrast to annual flowering in its country of origin; a phenomenon that has not been reported for the species before. The  ecological implication was discussed.

Key words: Cassia, correlation, flowering, phenology, rainfall, temperature.