The morning glory (Ipomoea nil), is one of the most successful of garden plants in Japan. Its local name is asagao (朝顔), literally “morning face”, but is another import from China. It may have been introduced for its medicinal properties – the seeds are toxic and were (and continue to be) used in Chinese herbal medicine as a purgative.
The local name is probably due the flower opening early in the morning. Each flower blooms for just one day.
A closely related, more recent import is the moon flower or moon vine, Ipomoea alba. Native to the sub-tropical and tropical Americas, it earns its place on this blog for its Japanese names and the nature of its blooming. The Japanese names yorugao (夜顔) or yugao (夕顔) mean “night face” and “evening face” respectively. The flower blooms in the evening, and is fully open after dark.
And just to make the patten complete, there is a plant in the same family locally known as hirugao (昼顔) – noon face!