Wisteria x formosa

Wisteria x formosa is an exceptional hybrid with incredible vigour. Its beauty surpasses that of its two parents, Chinese wisteria and Japanese wisteria 'Alba'. This climbing plant has an unruly temperament. It often flowers from a young age, unlike most of its cousins. In the heart of spring, its bare stems display beautiful clusters of flowers with two shades of mauve, spreading a deliciously sweet fragrance through the garden. This voluptuous wisteria needs space and sunlight. Grow it up a sturdy support, such as an old tree, a large arbour, or a long fence at the edge of the countryside.

Wisteria x formosa is a horticultural selection dating back to 1905, obtained in Massachusetts (United States). It is a hybrid of Wisteria floribunda 'Alba', native to Japan, and its cousin, W. sinensis, the vigorous Chinese wisteria. All these plants belong to the Fabaceae family. Like its ancestors, it is a robust plant, relatively resistant to cold, and not very demanding in terms of soil (although it fears an excess of active limestone). It can grow in poor soils that are dry in summer if they are deep. Its roots are deep and trailing, and its foliage is deciduous in winter.

Its voluble stems eventually reach a length of about 12 to 13m (39 to 43ft) and spontaneously wrap around supports clockwise. The growth of new silky shoots is very rapid, about 2m (7 feet) in one season in moist soil. Flowering takes place in May, at about the same time as that of Chinese wisteria. The flowers bloom on plants aged 2 years and older. They develop on slightly foliated branches located near the main lignified stems. The flowers take the form of pendulous clusters of strongly scented blooms with purple-mauve standards, wings, and keels, measuring 25cm (10in) in length. All the flowers open at the same time on the cluster. The flowers are nectar-rich and attractive to bees.

After the flowers, hanging flat green pods appear. They are swollen at the level of the seeds, and turn brown when mature. The young bronze-coloured leaves appear and then turn a light green. They are 20 to 30cm (8 to 12in) long and divided into 13 to 15 ovate leaflets, giving the foliage a light appearance. Before falling in autumn, the leaves take on a beautiful golden colour. It can live well over 50 years.

Wisteria x formosa is one of the largest in its genus and is suitable for a large garden. It will require repeated pruning to be kept in more modest dimensions. It adapts to all climates, including hot and dry ones. However, it will not withstand cold climates. This vibrant plant is particularly useful for dressing up a large wall or covering a long unsightly fence. It wraps around a sturdy arbour and climbs up to the tree tops if left to its own devices. As it tends to smother nearby plants, plant it on its own in full sun (or partial shade in hot climates). Alternatively, plant it with vigorous honeysuckles, clematis, or climbing roses.