Plant of the Month: May

Wisteria brachybotrys Murasaki-kapitan Common name: silky wisteria Family: Papilionaceae Vital statistics Height and spread: To 9m (30ft) and more Form: Deciduous climber Soil: Fertile, moist, well-drained soil Aspect: Full sun Hardiness: Fully hardy

Wisteria brachybotrys Murasaki-kapitan grows on the sheltered south-east wall of Rosemoor House, overlooking the old conservatory area. Also growing on Rosemoor House (on the south-west facing wall) is its more vigorous cousin, Wisteria sinensis. A selection of other wisterias can be found growing over the central arbour in the Potager.

Wisteria

A genus of about six species of twining, woody, deciduous climbers which can be found in moist woodland and beside streams in China, Korea, Japan and central and southern USA.

Cultivated for their showy, fragrant flowers which are borne in spring or summer. The individual pea-like flowers develop in long pendent racemes that have been known to reach up to 1.8m (6ft) in selected forms of Wisteria floribunda. The flowers are followed by bean-like, green seed pods in autumn.

Named for Caspar Wistar (1761-1818), professor of anatomy at the University of Pennsylvania and whose main interests, outside of medicine, were palaeontology and botany. He was one of the early owners of what is now Vernon Park, Philadelphia which is noted for its fine collection of rare trees and shrubs.

Wisteria brachybotrys Murasaki-kapitan

Often recommended as one of the most strongly scented wisterias it has deep blue-violet flowers with prominent white, slightly yellow-tinged markings. Each raceme of W. brachybotrys Murasaki-kapitan is about 20cm (8in) in length with approximately 35 to 47 individual flowers.

Brachybotrys is Latin meaning short-clustered in respect of the length of the racemes. Murasaki-kapitan is not treated as a cultivar name because it essentially means purple wisteria in Japanese and is used for a number of different forms. However, plants under that name in cultivation in the West are constant in their characters.

Little is known about how Wisteria brachybotrys Murasaki-kapitan was introduced into cultivation but it is believed to have reached the west when Philipp Franz van Siebold (1796-1866), a German doctor who visited Japan in 1823-1830 and 1859-1863, and introduced it to Ghent in 1830

Cultivation

Wisteria will grow in any fertile, moist, well-drained soil in full sun or partial shade, though they will flower more profusely in full sun. Traditionally wisterias are trained against walls, fences and pergolas but they can also be grown through large deciduous trees where their spring flowers can add interest before the plant's leaves are fully developed.

Given good soil conditions wisterias can establish rapidly but will need training to produce the best flowering display in a limited space, though specimens can be left to naturally grow through large trees where space is less limiting.

Prune initially to form a suitable framework. Once established prune to encourage the formation of flowering spurs, close to the main framework of the plant.

More details about pruning wisteria can be found in the advice pages.

Wisterias can be affected by several pests and diseases including leaf spot, aphids, brown scale and honey fungus.

Propagation

Wisterias can be propagated using basal cuttings from sideshoots in early to midsummer; encourage rooting by providing bottom heat. However, cuttings can take up to nine years to flower. Commercially wisterias are grafted so that older material is grafted onto a young rootstock thus producing a flowering plant much more quickly.

Plants can be raised from seed but are very variable, can take up to 20 years to bear flowers, and are usually inferior to named cultivars. Sow seeds in spring at 10-13ºC (50-55ºF) after soaking in hot water for about 18 hours. Take care however as the seeds are poisonous.