南中国の原産で、我が国への渡来は奈良時代とも平安時代ともいわれます。
初めは薬草として(牽牛子…けんごし)(けにごし)と呼ばれた。
一つひとつは朝咲いて昼を待たずにしぼんでしまいますが、夏から晩秋にかけて咲き続け朝霧を宿して先競うその姿は、いかにも涼しげで、暑い夏の朝を慰めてくれます。

朝顔 Asagao (Morning glory) is native to South China and have arrived in Japan during the Nara or Heian periods.
At first, they were called 'Kengoshi' (牽牛子...Kengoshi) as a medicinal herb.
As the name suggests, morning glories bloom in the morning and wilt before noon.
Blooming from summer to late autumn, the flowers look cool and provide a welcome distraction from the hot summer weather.