JAPANESE CULTURE, EXPLAINED
アサガオ
Japanese asagao cultivation centres on Ipomoea nil, an annual climbing morning glory. Alongside familiar funnel-shaped flowers, growers maintain forms with altered leaves, colours and petals. Some striking forms survive through careful selection across generations.
Cultivation can alter flower colour, pattern, leaf shape and the form of a bloom. Large-flowered strains and unusual henka asagao represent different horticultural interests. Exhibitions may also include related morning glories, making a named species or cultivar important when identifying a particular plant.
Kyushu University Museum explains a double-flowered example through fertile parent plants carrying a hidden variant. Their seeds can produce offspring displaying the sterile double flower. Maintaining the strain therefore means retaining the seed-producing parents that carry the variation.
There is no arrow from a sterile flower to seed; the example does not cover every cultivated variation.
The National Diet Library traces asagao’s arrival as a medicinal plant to the Nara period, before its later development as an ornamental in Edo horticulture. The National Diet Library describes waves of enthusiasm in the Bunka–Bunsei and Kaei–Ansei periods, followed by another in the later nineteenth century. Competitions, seed exchanges and illustrated publications circulated forms and growing knowledge. Plant dealers, individual growers and enthusiasts’ societies all helped sustain the culture.
Rekihaku describes a decline in unusual-form enthusiasts as large-flowered cultivation flourished from the Taishō period onward. A small number of growers and researchers maintained strains after World War II. Since 1999, the museum has displayed traditional morning glories alongside historical illustrated records, connecting living material with earlier descriptions.
Iriya offers a specific urban example. Taito Ward traces its reputation to local plant dealers in early Meiji, followed by an interruption in 1913 and revival in 1948. Its 2026 notice lists the fair for July 6–8 around Iriya Kishimojin. A cultivated potted flower thus also belongs to the seasonal life of a city market.
No. Leaf shape, petal form, pattern and flowering form can also be cultivated traits.
In the museum’s example, fertile parents carrying the variant produce offspring in which the sterile form appears again.
Taito records an interruption in 1913 and a revival in 1948.