The Wisteria is a long-lived, woody climbing vine with beautiful fragrant blue to purple flowers up to 36 inches in length. In spring and early summer, blooms appear on new growth and brown, bean-like pods develop on the plant after flowering. It is a very heavy vine that requires sturdy support. Wisteria is an aggressive, fast-growing plant that can easily reach lengths up to 30+ feet. Four types of wisteria are commonly available are: Wisteria floribunda (Japanese wisteria) – Wisteria sinensis (Chinese wisteria) – Wisteria fructescens (American wisteria) – Wisteria macrostachy (Kentucky wisteria).
| Note: All parts of the wisteria plant are deadly toxic to pets, livestock, and humans. |
Wisteria Cold Hardiness
Several types of Wisteria grow throughout Canada and the United States and each is slightly different in its cold hardiness. Some varieties are better suited for colder climates than others, but all thrive in full sun in milder temperatures. The Japanese Wisteria is hardy to about minus 30 degrees Celsius, while Chinese and American Wisteria are cold hardy to about minus 28 degrees. The most cold-hardy varieties are Kentucky Wisteria and “Summer Cascade” and “Blue Moon” which can sustain temperatures to minus 38 degrees Celsius.
Asian and North American Species
Asian wisteria plants are aggressive growers with fuzzy seed pods, while North American wisteria plants are not quite as aggressive in their growing habits and have smooth seed pods and fruits, as well as more-or-less cylindrical, bean-shaped seeds. Another difference is that American and Kentucky wisteria’s flowers appear after the plant has leafed out in the late spring, whereas the Chinese wisteria’s blooms appear before its foliage.
| Native wisteria, Wisteria frutescens, and Chinese wisteria, Wisteria sinensis, twine from left to right – clockwise, and Japanese wisteria, Wisteria floribunda, twines from right to left – counterclockwise. The spiral growth patterns can be a devastating strangulation to nearby trees and shrubs that come in contact with wisteria by robbing them of sunlight and nutrients. |
Wisteria Blooming & Not Blooming
Wisteria typically blooms within three years. Seed grown varieties should be avoided as they can take up to ten years or more to bloom. Several factors can lead to blooming failure: Too much shade, juvenile plants, late spring frost or improper pruning techniques. Another reason for failure to bloom can be excessive fertilizer, particularly nitrogen. Wisteria has nitrogen fixing capability and thus mature plants may benefit from added potassium and phosphate, but not nitrogen. Finally, the reason for no blooming can simply be – plant immaturity.
Wisteria can take a long time to bloom and first flowers may appear 2 to 3 years after planting. To expedite blooming startup, the plant can be shocked into reproduction by slicing some of the roots with a shovel. It is recommended to go about 8 to 10 inches into the ground about a foot and a half away from the main trunk. The chances to damage a wisteria by doing this are slim as it is a very resilient plant. Increased flowering has been achieved by some by adding liquid tomato or rose fertilizer.
Wisteria Growing Requirements
Wisterias prefer a deep and rich earth but they also tolerate dry and sandy soil. Their roots are long and only few go deep, making few fibers. Wisterias are hard to transplant, unless they have been pot-grown for the purpose. Slow growing speed after transplanting can be dramatically changed by adding composted manure. To give a young wisteria an extra-good start is to plant it in a bottomless tub filled with good soil. The best time to plant wisteria is when the plant is dormant – in spring or fall. For full flower development, the plant needs to be in full sun. Given its speed of growth, wisterias should be planted well away from other plants to prevent it from taking over and causing damage.
Wisteria Climbing Training
Dead trees make excellent supports for training wisterias to climb. Good results are to be expected only in sunny locations. The Japanese wisteria (W. floribunda) is one of the best climbers. Wisteria can grow into a mound when unsupported, but is at its best when allowed to climb up a tree or a very sturdy supporting structure like a pergola because it can grow into immensely heavy and thick trunks.
Wisteria Care
Adding a handful of bone meal to the soil in spring and phosphorus in the fall will aid with flowering. Removing rampant shoots every two weeks during the summer will encourage additional flowering. Regular watering is important as it ensures plant longevity, especially in arid regions. To retain moisture and to control weeds, compost worked can be worked into the soil together with a 2 inch layer of mulch.
Wisteria Pruning
Pruning is important for promoting better flowering and for controlling the size and shape of the wisteria plant. Regular pruning encourages the growth of new shoots, leading to more abundant and vibrant flowers. Wisterias grown too heavy can potentially damage structures such as pergolas or trellises. Wisteria should be pruned in mid-summer after flowering has finished and in late winter or early spring before new growth begins. Winter pruning helps to shape the plant, while the summer pruning encourages more blooms for the following year.
Dead or diseased wood should be cut back to healthy wood by making clean cuts just above a bud or lateral branch. To encourage new growth and shape, long lateral branches need to be cut back to 3 to 4 buds from the main stem. Excessively long shoots can be shortened to a length of about 6 inches. Branches that are crossing can cause damage over time and must be removed to maintain a clear structure. Summer pruning controls excessive growth and shaping the wisteria plant after it has finished flowering.
Wisteria Types
The main types are Asian and American varieties. Asian: Chinese wisteria (Wisteria sinensis), Japanese wisteria (Wisteria floribunda). American: American wisteria (Wisteria frutescens) and the Kentucky wisteria (Wisteria macrostachya). Asian varieties have showier, more colourful blooms than native American wisteria vines, but they are invasive.
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