Wisterias

The Beautiful Boa Constrictor of the World

Wisteria blossoms are pea-like.

A Chinese wisteria vine.

Wisterias become woody behemoths as they age.

Grow wisterias on sturdy supports.

Blossoms hang down like grape clusters.

A white wisteria seems to be engulfing this house.

It's not a good idea to grow a wisteria on a house.

An immature wisteria looking for support.

Wisteria flower buds open at the same time for a glorious display.

A stunning white wisteria.

Wisterias produce many vining stems.

A wisteria takes hold.

Wisteria buds are prone to late frosts.

A wisteria crushes a drain pipe.

Dangling Japanese wisteria seed pods linger throughout the winter.

Common Name: Japanese & Chinese wisterias
Botanical Name: Wisteria
Form: twining sprawling vine
Family: Fabaceae
Genus: Wisteria
Species: floribunda, sinensis
Plant Type: woody vine
Mature Size: depends on species
Growth: fast
Origin: Hardiness Zone:
Foliage: green, alternate, pinnate, 9-19 leaflets
Flowers: hanging racemes (clusters) of bright yellow pea-like
Fruit: velvety bean-like pods, numerous disk-shaped seeds, viable
Stems: young green tendril like that mature into woody, twining branches
Exposure: full sun
Soil: moist, well drained, fertile, dislikes too wet & too dry
Uses: plant on arbors, gazebos and free-standing supports
Attracts: bees & other pollinators
Invasive Tendencies: yes
Toxicity: all parts are poisonous if ingested
Tolerates: deer
Propagation: seeds, suckers
Pruning: after flowering and winter
Problems: invasive, aggressive, massive vines, crushes their support

Comments:

Wisterias are floriferous woody vines that bear a plethora of large dangling grape-shaped clusters of blossoms in May and June. Their dramatic flower displays are spectacular, but beware, they are fast and aggressive growers. Wisterias are high maintenance as they must be controlled so they don’t take over the garden and house

Wisterias have a reputation as the boa constrictors of the garden world. They wrap around anything they touch and slowly crush them. Their thick woody stems start out as soft green sinewy tendrils that eventually mature into mighty lianas that crush downspouts, eaves, arbours, nearby plants and anything in their wake. Because of wisteria’s ability aggressive nature, it is recommended to grow wisterias on arbours, trellises, pergolas and gazebos, not the house and anything else that you don’t want crushed.

Japanese and Chinese are the most common types of wisterias. Although they look similar there are a few distinctions. Chinese wisteria vines twine counterclockwise, while the Japanese species twirl clockwise. Flowers of both species appear in May on bare stems just before leaves appear. They need full sun as shade inhibits flowering. Wisterias prefer moist, slightly acidic, well-drained soils but are relatively tolerant of any soil as long as it’s not too dry nor too wet.

Japanese wisteria, W. floribunda has the longest flower clusters up to 3 feet with some cultivars up to 47 inches in length. Their fragrant pea-like blossoms are purple, pink, blue, red or white depending on the cultivar, which there are many. Japanese wisterias are a much larger vine than the Chinese type as they can grow to a whopping 98 ft in length! Their vines twirl clockwise around their supports and bare shiny dark green pinnate (feather-like) leaves. The foot long foliage consists of 15 to 19 oblong leaflets, each up to 2.5” long. Velvet 6” long pendulous seed pods follow the blossoms. They ripen in autumn but persist into winter. With judicious pruning Japanese wisterias can be trained into small trees. USDA Zones 4 to 9.

Chinese wisteria, W. sinensis: Vines twirl counterclockwise and grow to 25 feet in length with a spread of 8 feet. Foliage is deep green and compound with 7-13 leaflets and pinnate (feather-like). They bear scented flowers up to 12” long in mauve or white, depending on the variety. Flowers are followed by flattened, brown, velvety, bean-like 4”-6” long pods. The pods twist open to release their seeds in summer, however their empty dangling pods persist into the winter. They produce fewer seed pods than the Japanese wisteria. Despite the low seed production Chinese wisterias are invasive. They not only produce suckers, their stems often root when they come in contact with the ground. USDA Zones 5 to 8.

Wisterias That Fail to Flower
There are numerous reasons why wisterias don’t flower. Immature wisterias, especially ones grown from seed, need to fully mature to blossom. To stimulate flowering, use a shovel to cut all around the plant, approximately 18” to 2’ from the main stem. Just sever the roots, don’t dig them up. Follow up by watering thoroughly.

Mature plants don’t flower when late frosts kill the vulnerable buds. Other reasons include too much shade, pruning at the wrong time of year, pruning too severely and applying too much nitrogen.

Pruning
To tame these boa constrictors of the plant world, prune them twice a year; once in winter and again right after they finish flowering. When pruning wisterias, do your best to figure out where the main stems are. This is difficult to figure out if there are many stems so look for the biggest ones that are growing in the direction you want them to grow. Once you figure out which are the main branches, remove all minor branches and cut back the side stems from the remaining vine. Don’t remove them entirely, just cut them back to 2 to 4 buds. These little stubby stems should convert to flowering spurs within a couple of years. This also helps to control their growth whilst producing more flowers.

Toxicity
All parts of wisterias are poisonous if ingested.