Bougainvillea typically flowers in cycles from late autumn to early spring in tropical and subtropical climates (roughly November to May). In cooler temperate regions, it blooms heavily in late spring and summer (May to September).
However, with the right care, many varieties will bloom , with each bloom cycle lasting 4 to 6 weeks. Detailed Guide by Climate & Season Bougainvillea is a tropical vine, but it adapts to different climates, which changes its bloom time. when does bougainvillea flower