Wisteria

Wisteria is a showy, woody vine that blooms in mid-spring and will grow to 10 to 25 feet, depending on the support it is given. There are four species in the genus, three native to eastern Asia and one native to the eastern USA. The genus name honors Caspar Wistar (1761–1818), an American physician and anatomist on the faculty of the University of Pennsylvania. 

Wisteria species are readily adaptable to most soil types and moisture conditions. They flower best in full sun. Wisterias (especially the Asian species and cultivars) should be pruned twice a year to manage growth and promote air circulation (to prevent disease). In mid-summer, after the plants have flowered, cut back long, whippy shoots to five or six leaves. This will restrict further growth in the summer and autumn. In January or February, when the plants are leafless, trim the shoots you cut the previous summer to just two or three buds. Also, remove dead wood and cut back any whippy shoots missed in the summer. This will encourage spur formation and flowering. 

Although wisteria can be grown from seed, it may take several years to mature and produce flowers. Most cultivars are grafted, and it’s a good idea to buy plants in flower, so that you know the plant is old enough to make flowers. Wisteria blooms are highly fragrant and come in a variety of colors, ranging from pink to purple to white. These flowers are found in long drooping clusters up to 18 inches in length. Training into a small tree or shrub requires a significant amount of pruning and effort. 

The commonly cultivated Asian species (Wisteria sinensis and Wisteria floribunda) and their hybrid have the potential to outcompete the host trees for sunlight. Left to grow at will, the Asian species become aggressive pests in the landscape, and they can escape into natural areas. The American wisteria (Wisteria frutescens) is much less aggressive and requires less pruning and poses no risk to natural areas. When choosing a plant, please consider the fact that Asian wisterias are more aggressive growers than the North American species. Distinguishing traits include differences in the seed pods. Asian wisterias have fuzzy seed pods, while North American wisteria has smooth seed pods. Also, the flowers on the North American varieties bloom after the plant has leafed out, while Asian wisterias will bloom before the foliage opens. This plant is mildly resistant to damage by deer and is toxic to dogs, cats and horses. 

Wisteria is a classic climber for cottage gardens and Asian gardens. The American species can be used in a native plant garden, pollinator garden or butterfly garden. Wisterias add a romantic elegance to arbors and pergolas, and they can be stunning accent plants in the landscape.

Insects, Diseases, and Other Plant Problems: Due to their rampant growth, some wisterias can become quite heavy, putting a strain on the pergola or structure supporting it. Make sure the support can handle this heavy climber. Wisteria can grow into small spaces and pry them apart as it grows, so allowing it to climb your home is not advisable. It could easily damage rain gutters, shutters, awnings, etc.  Some insects affecting this plant are Japanese beetles, aphids, leaf miners, scale insects and mealybugs. Dieback, crown gall, and leaf spot are some diseases known to affect wisterias.