There are two Wisteria species of particular value in the garden, both twiners with trails of scented, pea-typein spring, but differing in vigour and flower character. The Chinese wisteria, Wisteria chinensis, is the kind usually seen covering house fronts or climbing high into trees. It is a very vigorous plant capable of reaching Soft. or even more and its flowers, blue mauve in the common form, are in trails 9 to 12 in. long. There are also white and double-flowered varieties. The Japanese wisteria, W. floribunda, is less vigorous, usually about 12 ft. high and often trained as a kind of small weeping ‘tree’. In general the flower trails are a little shorter, but one remarkable variety, macrobotrys, has trails up to 3 ft. long. This variety is the typical blue purple of the species, but there are also white, pink and violet-blue varieties.
Wisteria sinensis (Chinese witeria) is the most popular species: not surprisingly, for it is the tallest – up to 18m (59 ft) and the most fragrant and spectacular, the long racemes of mauve flowers appearing in May before the, with a second flowering in warm summers in early August. There are several cultivars, including ‘Plena’ (double flowers) and ‘Alba’ (white flowers). W. floribunda (Japanese wisteria) is similar, but not so vigorous, growing up to 9 m (30 ft).
Since it was introduced to Europe in Victorian times many cultivars have been produced, some with extra-long racemes of flowers, including ‘Rosea’ with pink racemes 45 cm (18 inches) long and ‘Macrobotrys’, whose purple racemes are 90 cm (3 ft) long. These look best when they are trained over an arch or pergola so that the racemes of flowers hang down clear of the plant. W. venusta grows up to 7.6 m (25 ft), and has the largest flowers of all, but the racemes are not particularly long.
General care: All wisterias prefer a sunny site, such as a south-facing wall, except for W. floribunda, which will tolerate some shade. They like a rich moist soil with plenty ofdug into it. The young plants can be put in at any time during the winter, and need support until they can start twining and climbing. Eventually wisteria will grow into a self-supporting tree with a head of new young growth. in December, the laterals back to three buds from the base of the previous year’s growth.
Propagation: Wisteria can be grown from, but the results are seldom satisfactory. It is best to take 10cm (4 inches) long of the current year’s growth in August, and strike them in a 50-50 mixture of peat and sand.
Pests and diseases: Birds may eat the flower buds; so net the trees in winter. Bud drop is caused by lack of water.
All wisterias grow best in warm, sunny places and fertile, well-drained soils. They transplant badly and should be purchased young in containers, moved from these withoutbreakage and watered and syringed frequently in hot dry weather until established. They can be pruned in summer when all young growths not required for extension can be shortened to five leaves and again, if desired, in winter when the same growths can be cut back to two dormant buds. When the plants have filled their allotted space all surplus growth can be cut out each winter.