Like many others, I plant moonflower (Ipomoea alba) in the early summer to fill a small trellis with a quickly growing annual vine. I anticipate the large, round and fragrant flowers, but most of the summer goes by without any sign of a bloom. I’m not alone. I know from calls to the radio station and emails to Plantrama that people wonder why some of their plants take so long to flower.
In fact, my moonflower, and several other plants, are simply showing signs of photoperiodism. Ellen and I discussed this in an episode of Plantrama recently. Basically, photoperiodism is an organism’s response to the hours of daylight. Or, as in this case, the hours of darkness. Because my moonflower doesn’t come into bloom until the hours of daylight decrease and the hours of darkness increase.