7-9 o'clock. According to the information of agricultural official website, rape blossoms generally start to bloom between 7-9 am, and bloom at noon 12 or so, and then fade gradually. Rape flower is a kind of plant with short photoperiod, which needs light to bloom. The sunshine in the morning is softer, which stimulates the flowering of rape, so it will start to bloom in the morning. The flowering temperature of rape flowers is relatively high, generally at 15-20℃. The temperature is low in the morning, but it gradually rises after the sun rises, which is in line with the temperature conditions of rape flowering. The flowering of rape flowers needs a certain humidity. Too low or too high humidity will affect flowering, and the humidity in the morning is more suitable.