Culture
Best grown in slightly acidic, humusy, moderately fertile, medium moisture, well-drained soils in full sun. Full sun is needed for best flowering. Can be invasive (rampant growth plus rooting surface runners). This vine needs space and a sturdy support structure on which to grow. It can be slow to establish. Although vines may produce flowers by the second or third year after planting, it may take much longer (sometimes up to 15 years). Plants grown from seed may take up to 20 years to flower. Needs regular pruning(s) in order to control size and shape of the plant and to encourage flowering, such as a pruning back of stems (a) in early summer after bloom and (b) in winter. Root pruning in late fall may also stimulate flowering for the following spring. Improper pruning may overly stimulate vegetative growth at the expense of flowers. Consult a pruning guide for specifics on the initial training of vines and the types of pruning that can or should be done for these high maintenance plants. An application of superphosphate in early spring can also help stimulate flowering. Choose growing sites wisely because plants dislike being transplanted.
Noteworthy Characteristics
Wisteria sinensis, commonly called Chinese wisteria, is a deciduous vine that grows vigorously to 25’ or more and features 6-12” long racemes of mildly-fragrant, pea-like, blue-violet flowers in May when the foliage is just beginning to expand. Flowers bloom somewhat simultaneously on the racemes thus producing a dramatic floral display. Flowers give way to pendant, velvety, bean-like seed pods (4-6” long) which ripen in autumn and may persist into winter. Compound, odd-pinnate, deep green leaves (each leaf typically with 7-13 leaflets). In contrast to the very similar Japanese wisteria (Wisteria floribunda), Chinese wisteria differs by counterclockwise twining, fewer leaflets per leaf, shorter flowering racemes of less fragrant flowers that bloom simultaneously on each raceme and blue violet flower color. Over time, the stems of this vine become twisted, trunk-like and massive.
Genus name honors Caspar Wistar (1761-1818), professor of anatomy at the University of Pennsylvania.
Specific epithet means Chinese.
Problems
Although susceptible to a number of foliage-chewing insects and fungal diseases, none are significant. It is considered to be a high maintenance plant, however, because of its need for regular pruning, its invasive tendencies and its vulnerability to late spring frost damage to flower buds. Failure of vines to produce flowers may be attributable to a number of causes including death of flower buds in winter, too much shade, plants too young (especially seed grown ones), improper pruning or overfertilization.
Uses
Plan ahead when planting this vine. It must be sited and trained only on sturdy structures which will be able to support the considerable weight of the mature vine. This is an excellent vine for large, sturdy, freestanding arbors, pergolas, posts, trellises, fences or terrace walls, and can be particularly effective when grown near or above patios where the flowers can be enjoyed in season. May also be trained as a specimen shrub or tree.