I don't think that
Japanese morning glories are any different from morning glories elsewhere. They twine and climb, they flower here as there. But asagao are a strong thread in the weave of Japanese culture.
Grown since ancient times, asagao (the morning glory flower) is one of the most popular of
summer garden plants in Japan.
Originally brought to Japan around the 10th century from China for medicinal purpose, asagao have captured the heart of the Japanese people by their lovely flowers, and have been the inspiration for many Japanese poems. Asagao is definitely symbolic of summer in Japan. A great number of people find an oasis in their minds in looking at asagao in the morning before dealing with the excruciating summer heat as the day proceeds.
There is an asagao fair held annually in early July around Kishibojin temple in the Iriya district of Tokyo. In the Edo period the cultivation of asagao became very popular, and asagao experts (called asagao shi) produced a large number of new varieties. Many of these specialists lived around Iriya and during blooming season, they brought their own hybrids and had contests. That was how the fair got started. To this day, it's still an event of the summer season.