What is a Japanese Wisteria?

Japanese wisteria, also known by its scientific name, Wisteria floribunda, is a vigorous climber that is native to Japan. Introduced to the United States in the 1830s, in many areas it has escaped from cultivation and has become an invasive weed. It is most often planted for its fragrant flowers and its ability to climb over an arch, up a wall, or around a large tree. If it is consumed, it is toxic.

The leaves of the Japanese wisteria are typically pinnate, or located on opposite sides of a stem. Usually, there are ten to 20 leaves per stem that are lance or oval-shaped, depending on the variety. The flowers are usually blue, violet, pink, or white and are incredibly fragrant. The flowers grow in long racemes, or clusters, that can be well over 12 inches (about 30.5 cm) in length. This species of climber may also produce a bean pod that grows to approximately 6 inches (15.2 cm) long.

The perfect habitat for Japanese wisteria is in full sunlight, but vines that are already established can thrive in partial shade. They have such an affinity for sunlight that they will climb over any obstacle in its way to reach it. In addition, it is able to tolerate a wide range of soil types and moisture levels.

Although many gardeners plant Japanese wisteria because of its beauty, it has also become invasive in many areas. It is capable of growing extremely dense thickets. As a result, it constricts the stems and trunks of trees and other plants and kills them. It is also known for growing over the tops of the tree canopies, killing them, to reach more sunlight.

There are a few methods to control Japanese wisteria. For example, the vines can be cut close to the root to prevent strangulation of other forms of vegetation and stop seed production. In addition, if the root is removed through a technique called grubbing, it will prevent the vine from re-sprouting. Certain herbicides can also be applied to the vine to kill it at the root, particularly in areas where it has invaded the canopy of other woodland trees.

The flowers, bean pods, seeds, leaves, bark, and roots of the Japanese wisteria are all toxic. In fact, if a child were to consume a single seed, it could result in serious ramifications, such as poisoning. Symptoms of poisoning include vomiting, nausea, diarrhea, abdominal pains, and collapse.