1248 Wisteria floribundaCommon Names: Japanese wisteria Family: Fabaceae (bean Family)
Japanese wisteria is a vigorous twining vine that will climb on anything it can reach and get up to 50 ft (15 m) or more in length. Older stems become woody and can be as much as 3-4 in (7-10 cm) in diameter. Japanese wisteria has deciduous odd-pinnate leaves around a foot (30 cm) long, each with 13-19 leaflets. Compare Japanese wisteria to Chinese wisteria (Wisteria sinensis), which has just 7-13 leaflets. Also note that Japanese wisteria vines spiral clockwise, whereas Chinese wisteria vines spiral counter-clockwise. In late spring, as the leaves emerge or a little before, Japanese wisteria blooms with pendant racemes of fragrant pea-like flowers that may be blue, violet, pink or white. Each flower has little white and yellow markings on its standard (the uppermost petal). The showy flower clusters of Japanese wisteria are 12-20 in (30-50 cm) long, whereas those of Chinese wisteria are just a foot (30 cm) long or less. The individual flowers in each cluster open gradually, beginning at the base. Flowers are followed by velvety green flattened pods around 6 in (15 cm) long.
Cultivars of Japanese wisteria include ‘Alba’, which has white flowers in large racemes to 24 in (60 cm) long; ‘Honko’ with pink flowers; ‘Royal Purple’ (aka ‘Black Dragon’) with purple flowers; ‘Violaca Plena’(aka ‘Double Black Dragon’) with double bluish violet flowers; ‘Rosea’ with deep pink to almost red flowers; and the spectacular ‘Macrobotrys’ whose racemes of lilac-blue flowers can be 3-4 ft (0.9-1.2 m) long.
Wisteria floribunda is native to Japan, but has escaped cultivation and become weedy in many parts of the world including North America, where it is established from New England, south to Florida and west to Texas. In its native range, Japanese wisteria occurs along stream banks and in open, moist woodlands.
Light: Wisteria thrives in full sun and tolerates partial shade. Best flowering comes from plants in full sun. Moisture: Japanese wisteria thrives in a moist but well drained soil, and is surprizingly tolerant of drought when it has to be. Hardiness: USDA Zones 5 - 9. Propagation: Basal cuttings taken in spring from young, fast growing stems are fairly easy to root. New plants also may be started by layering, which usually is quite effective. Plants grown from seed take many years to reach flowering age. Cultivars are grafted onto seedlings.
Japanese wisteria is popular for its huge, very showy flower clusters that can get up to 20 in (50 cm) or more in length. It is not quite as fragrant as the related Chinese wisteria, but every bit as pretty. Japanese wisteria blooms earlier in spring than Chinese wisteria, and this makes it more vulnerable to a late frost which would inhibit flowering (but not kill the plant). The wisterias are popular vines for pergolas, gazebos and similar trellis-like structures that can best display their pendulous sprays of colorful fragrant flowers.
All of the wisterias must be aggressively and repeatedly pruned to keep them in check. They can be trained on virtually any structure, but our favorite method is to prune them into a standalone shrub or tree-like shape.
The wisterias are very popular with pollinating insects, especially bees and butterflies.
Members of the subfamily that includes the genus Wisteria have elaborate pea-like flowers in which one petal forms a hood (the standard) over four other petals, two of which form lateral "wings," and two of which are fused together to form a keel. There are some nine or ten species of Wisteria, native to eastern Asia and eastern North America, a not uncommon distributional pattern.
Japanese wisteria, like its close relative, Chinese wisteria, can be extremely invasive. Both species can smother the trees they climb on and their sheer weight can cause damage to structures such as your home. Vines have been known to tear shingles and siding off the sides of houses. The oriental wisterias often branch out near or just under the ground, sending out runners that can quickly overwhelm nearby vegetation. The root systems can damage concrete foundations and slabs, as well as underground pipes. Both Japanese and Chinese wisteria are considered invasive exotic pest plants by concerned organizations. The prudent gardener would be well advised to select a species native to his region. For North American gardeners, we recommend the much better behaved American wisteria (W. frutescens) or Kentucky wisteria (W. macrostachya).
Steve Christman 12/10/15