Japan’s floral symbol of summer, the asagao (morning glory; Ipomoea purpurea) is an interesting climber with beautiful blooms that has been cultivated on these islands for more than 1,000 years since being brought from China during the Nara Period (710-784). Before that, its origins are a matter of some debate, with many believing the family Convolvulaceae (of which it is part) is native to tropical Asia, and others pointing to tropical America instead.
Annuals that became very fashionable during the Edo Period (1603-1867), when hybridizing them was also popular, asagao were often depicted in screen paintings. However, their appeal is not merely historical, and every year schoolchildren throughout the country still take a great interest in planting their seeds in spring, generally in pots with some trellising for the vine to climb on.
Asagao are ideal for children to study, as once the seeds germinate the plants grow rapidly and soon begin flowering. This rapid development captivates children, and helps instill in them an interest in plants and nature.
Should they take a liking to asagao in particular, there’s plenty of scope for following their interest. Altogether, there are estimated to be 650 ipomoea species throughout the tropical and warm-temperate regions of the world, and apart from the aforementioned annuals, numerous other types are grown and easily available in Japan. Among these, perhaps the most popular is the cultivar Heavenly Blue, which has heart-shaped leaves and reddish flower buds, though according to the soil’s pH level, the funnel-shaped, 4- to 6-cm diameter blooms generally change to various shades of blue.
Another pretty asagao I came across growing on an empty lot last summer was maruba-ruko (red morning glory; I. coccinea). Native to tropical America, this was introduced to Japan between 1848-54 — originally as cattle fodder. However, the seed passed through the cows intact, and was then dispersed in their dung. The 1.5- to 2-cm-diameter, trumpet-shaped flowers of maruba-ruko are scarlet on the outside and yellow on the inside. A further point of interest is that after flowering starts in August, they bloom more profusely as the days shorten right through to October.
It’s interesting to think, too, with this species now naturalized in the Chubu region and westward on Honshu, that we have cows to thank for such a pleasing summer show that’s also ideal for growing on an arch or chain-link fence in full sun.
An ipomoea that is especially popular with gardeners is yoru-gao (moonflower or belle de nuit; I. alba), whose species name “alba” (meaning “white”) derives from its massive, 15-cm-diameter white flowers. As its Japanese name suggests (“yoru” means “night”), this species flowers from dusk through the night — or on cloudy or dull days, too — exuding a fantastic scent all the while.
A native of tropical America, yoru-gao — which was introduced to Japan during the early Meiji Era (1868-1912) — is one of my favorite ipomoeas, all the more appealing because it is perennial where the winters are very mild, and can also be grown indoors in cooler areas, flowering from August through October.
Another dusk-flowering plant that is both cultivated and naturalized in Japan is oshiroi-bana (common 4-o’clock plant; Mirabilis jarapa). As the name suggests, this species’ slightly fragrant, trumpet-shaped blooms begin to open at about 4 p.m., from August through September. Also native to tropical America, oshiroi-bana’s flowers range from white through red, pink and yellow, with numerous shades in between.
Propagation of this species — and most other asagao — is by seed, sown in May. Prior to sowing, soak the seeds in water for two days, or chip them with a sharp knife to speed up germination. Choose a sunny position and ensure the soil has good drainage.
Meanwhile, garden centers have recently started selling perennial asagao. One of these is called Capetown Glory and, on a recent visit to the very interesting Kobe Parks and Greenery Association center ( www.kobe-park.or.jp or call  351-6756) near Sorakuen Garden in Chuo Ward, I chanced on one of these growing right up the 5-meter fence around a baseball field — a magnificent specimen that staff at the center told me was only two years old.
Capetown Glory is probably a cultivar of no-asagao (blue dawn flower; I. indica), which in Japan grows near the shores of islands in the Izu archipelago, on the Kii peninsula in southern Kinki, in Shikoku and around the southern tip of Kyushu. Despite it prodigious growth potential, however, the plant is almost incapable of producing seed — a characteristic known as self-incompatibility. As a result, taking stem cuttings seems to be only way to propagate this plant. These can be taken during summer, put into a small pot and covered with clear plastic. Once rooted, remove the plastic, stand back . . . and watch it grow. You will notice that this no-asagao has two types of leaves, one heart-shaped and the other with three lobes, but both fall off in winter. It also bears lovely 10-cm diameter bluish-purple flowers from June until December — and if you, too, have a chain-link fence in a sunny position, you may like to try adding a little Capetown Glory to your life.
In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.