Wisteria sinensi blue or Chinese wisteria blue, is a twining, woody vine found in moist woodland and on stream banks in China, Korea, Japan, and central and southern USA. It is a fast grower with stems to 25 feet or longer if grown in the wild.
Wisterias do not conform to normal bonsai styling; they are styled to show off their highly scented racemes of flowers up to 30 cm long. Flowers appear in late Spring or Summer. This deciduous vine is awesome in springtime as it leafs out and flowers with large, drooping racemes, grapelike clusters of purple-blue, fragrant flowers. The flowers are followed by attractive velvety pods 6 inches in length, containing the seeds.
The long dark green leaves are suitable for bonsai styling as they are made up of 7 to 13 smaller leaflets that are around 5 cm long.
This plant is often grown with multiple trunks but it can be trained to a single trunk as a bonsai. Chinese Wisteria is usually very long lived and trunks can become quite large with age. With constant pruning, Wisteria can be trained to a small tree or bonsai-like specimen plant. This repeated pruning also encourages dense, compact foliage and flowering.
Hardiness zones 5-9, (-5°C/25°F, -26°C/-15°F) in Winter. Due to the high moisture content of the roots, it should be given some protection when temperatures drop below -5°C. It is not fussy about soil type or moisture, although its preference is a reasonably moist, well drained, rich to average mix. Full sun or partial shade.
Wisteria require large quantities of water in comparison to most other bonsai species and need heavy watering to keep them continually moist. In periods of hot weather during the Summer, they will happily tolerate their pots being stood in a shallow tray of water to keep up moisture levels. However, water trays, if used, should be allowed to dry out daily. Water heavily before and during flowering.
In general, Wisteria need more fertilizer than most bonsai. However, in order to ensure good flowering, feeding should be minimized during and immediately following flowering. Fertilize heavily in Spring before flowering and in late Summer and Autumn, until the leaves drop.