一、洋蔥的開花期（Blooming date）始自種球（Mother bulb）定植後80天，開花盛期則為104天。開花期間平均約為48天左右，在本省南部氣候下開花盛期約自2月下旬∼3月上旬。
Studies on Flower Behavior and Pollination in Onion (Allium cepa, L.) in Taiwan
M. T. Chang
1. The blooming period of onion is from first February to late March in southern part of Taiwan.
2. The flower of onion can open within 24 hours. The highest number of open flowers is 73% at 9:00am ~ 5:00 pm, second is 21% in the morning, third is 6% at night.
3. The anthers of 3 inner stamens are first to dehisc that are 27 hours after the flower opened and shed their pollen 24 hours after that. After the inner whorl of anthers has shed its pollen, the anthers of outer whorl of stamens dehisc and shed their pollen 27 hours after that. So, the pollen period of 6 stamens is 51 hours long.
4. The style is approximately 1 mm long and the stigma still immature when the flower first opens. It continues to elongate until reach its maximum length of about 5.5 mm. That is 84 hours after flower opens and all pollens is shed before the stigma becomes receptive. The stigma may extend a period of about 108 hours to have a receptability.
5. The best time to have a good receptability of stigma is at sixth day after flower open.
6. The blooming period of an inflorescence may extend 48 days and at 25~28 days can have a highest fruit setting under open pollination.
7. Different pollination methods can mostly influence on fruit setting under self-fertility. The highest fruit-setting is 81% with force pollination, second is 64.3% with open pollination, forth is 43.0~54.6% with house fly or bee pollination, fifth is 16.7% with feather pollination one time 3 days, sixth is 14% with feather pollination one time 2 days, seventh is 11.2% with feather pollination one time one day.