The main function of a flower is to attract pollinators so that they can bring about pollination. Plants flower at a time when their pollinator is most active. For example, flowers of the sausage plant are pollinated by bats. And bats are awake at night so this plant flowers at night. Also flowering in plants is related to the length of the day. This phenomena called photoperiodism classifies plants as short-day plants (chrysanthemum) and long-day plants (wheat).
- Because their biological clocks have fixed flowering alarms.
- To keep their appointments with insects who pollinate them.