Japanese wisteria (Invasive Plants of Maryland)

Japanese wisteria

Wisteria floribunda

Description ⁶

Japanese wisteria is a deciduous, woody ornamental vine that climbs trees high into the canopy, to more than 60 feet. It twines upwards in a counter-clockwise direction. The stems are slender, brown and densely pubescent when young, becoming hairless with age. Older plants can grow to 15 in. or more in diameter. The leaves are alternate and compound, 8-12 in. long, with 7-17 (19) leaflets which are egg-shaped and have slightly wavy margins. In the mid-Atlantic region flowering occurs in April before the leaves expand. Flowers are violet to violet blue, occur in pendulous racemes (clusters) 1-3 ft in length and open sequentially from the base to the tip. The flowers are 0.6-0.7 in. long on stalks (pedicels) 0.6-0.8 in. long. Fruits are velvety pods 4.5-7.5 in. long, broader towards the tip, and contain 3-6 glossy orbicular violet purple seeds each about 0.5 in. across. The pods begin to appear soon after flowering, mature during the summer and may persist for quite a while on the vines.

NOTE: Look-alikes: 1) American wisteria (Wisteria frutescens), native to the southeastern U.S. into southern Virginia, twines clockwise, stems brown to reddish brown and hairless, leaves with 9-15 leaflets, lower surface somewhat milky green, flowers in May after the leaves have expanded, flower clusters are 1.5-6 in. long, shorter than both Chinese and Japanese wisteria, flower pedicels 0.2-0.4 in long, seedpods 2-4 in. long, brown and smooth (non-hairy); 2) Chinese wisteria (Wisteria sinensis) also twines clockwise; stems are stout, gray-brown and covered with fine white hairs; leaves have 9 to 11 (7-13) leaflets; flowers are lavender to purple in racemes 6-8 in. long and open mostly all at once; flowers are 0.8-0.9 in. long on stalks (pedicels) 0.6-0.8 in. long; 3) trumpet creeper (Campsis radicans) native to central and eastern U.S.; has opposite leaves with toothed leaflets and orange-red flowers that bloom from late spring through summer and into fall.

Ecological threat in the united states ⁷

The hard woody vines of Japanese wisteria twine tightly around host tree trunks and branches and cut through the host tree bark, eventually girdling and killing it. On the ground, new vines germinating from seed or sprouting from rootstocks form dense thickets that smother and shade out native vegetation and impede natural plant community development. As girdled trees die, canopy gaps are created which increase the amount of sunlight reaching the forest floor. While this may temporarily favor some native species, it also stimulates vigorous growth and spread of wisteria.

Impacts and control ⁸

More info for the terms: cover, fire management, hardwood, invasive species, prescribed fire, presence, restoration, vine, vines

Impacts: Information regarding the impacts of wisterias on invaded communities includes evidence that both species displace existing vegetation by strangling or shading out native plants and trees [17,21,30,34,35]. The death of large trees from wisteria establishment results in breaks in closed canopy forest, which favors further growth and spread of wisteria [17]. Once established in an area, wisteria patches can potentially cover several acres; one herbicide experiment in Alabama was conducted in a Chinese wisteria patch that covered 2 to 3 acres (1 ha) [22]. The presence of Chinese wisteria was listed as a problem in the restoration of bottomland hardwood forests in Mississippi [32] and threatens old-growth remnant stands of longleaf pine in the Southeast [40]. Chinese wisteria is also listed as occurring on National Wildlife Refuges in Florida [16].

While both wisteria species are listed as invasive species of concern in a number of states, information as of 2009 suggests that they are less of a perceived threat than other, co-occurring invasive species [23,29,37,44]. For example, in a paper describing woody invaders of eastern forests, Japanese and Chinese wisteria are not considered as much of a threat as other woody vines, including Oriental bittersweet (Celastrus orbiculatus), Japanese honeysuckle (Lonicera japonica), or kudzu (Pueraria montana) [44]. However, that status may change in the future.

Control: In all cases where invasive species are targeted for control, the potential for other invasive species to fill their void must be considered, no matter what method is employed [5]. Information presented in the following sections may not be comprehensive and is not intended to be prescriptive in nature. It is intended to help managers understand the ecology and control of wisterias in the context of fire management. For more detailed information on control of Japanese or Chinese wisteria, consult the references cited here or local extension services.

Fire: For information on the use of prescribed fire to control this species see Fire Management Considerations.

Prevention: No information is available on this topic.

Cultural: No information is available on this topic.

Physical and/or mechanical: One review outlines strategies for cutting climbing or trailing vines of Japanese wisteria. Wisteria can sprout numerous times after cutting, so the treatment must be repeated until root stores are exhausted. If done approximately every 2 weeks from spring until autumn, cutting prevents seed production and strangulation of surrounding vegetation. This type of treatment is appropriate for small populations, as a pre-treatment for large, impenetrable sites, or in areas where herbicides are not appropriate [30].

It is also possible to try to control juvenile or isolated Japanese wisteria plants using a pulaski or similar digging tool to remove the entire plant, including all roots and runners. Any portions of the root system not removed are capable of sprouting. This treatment is appropriate for small initial populations or areas where herbicide use is not feasible [30].

Biological: No information is available on this topic.

Chemical: A range of foliar spray herbicides has been effectively used for wisteria control [22,30], though high rates and repeated applications were needed to produce near-eradication [22] and it was possible to damage non-target species with treatment. Cut-stump application of glyphosate or triclopyr 2 inches (5 cm) above ground level was also found to be effective for Japanese wisteria control, though foliar spray treatments may be needed afterward to compensate for the stimulation of wisteria seedlings after large vine removal [30]. Care must be taken when other invasive species are present; in one herbicide treatment, the reduction in Chinese wisteria cover released the invasive Chinese privet (Ligustrum sinense), which was not impacted by the herbicides [22].

Integrated management: No information is available on this topic.

Wisteria floribunda ⁹

W. floribunda growing in Longwood Gardens

Wisteria floribunda - MHNT

Wisteria floribunda (common nameJapanese wisteria) is a species of flowering plant in the pea family Fabaceae, native to Japan. Growing to 9 m (30 ft), it is a woody, deciduous twining climber. It was brought from Japan to the United States in 1830's.^[1]^[2] Since then, it has become one of the most highly romanticized flowering garden plants. It is also a common subject for bonsai, along with Wisteria sinensis (Chinese wisteria).

The flowering habit of Japanese wisteria is perhaps the most spectacular of the Wisteria family. It sports the longest flower racemes of any wisteria; they can reach nearly half a meter in length. These racemes burst into great trails of clustered white, pink, violet, or blue flowers in early- to mid-spring. The flowers carry a distinctive fragrance similar to that of grapes. The early flowering time of Japanese wisteria can cause problems in temperate climates, where early frosts can destroy the coming years' flowers. It will also flower only after passing from juvenile to adult stage, a transition that may take many frustrating years just like its cousin Chinese wisteria.

Japanese wisteria can grow over 30m long over many supports via powerful clockwise-twining stems. The foliage consists of shiny, dark-green, pinnately compound leaves 10–30 cm in length. The leaves bear 9-13 oblong leaflets that are each 2–6 cm long. It also bears numerous poisonous, brown, velvety, bean-like seed pods 5–10 cm long that mature in summer and persist until winter. Japanese wisteria prefers moist soils and full sun in USDA plant hardiness zones 5-9.^[3] The plant often lives over fifty years.

§W. floribunda cultivars[edit]

Those marked agm have gained the Royal Horticultural Society's Award of Garden Merit.

'Shiro Noda', 'Snow Showers' or 'Longissima Alba' agm^[4] - long white flower clusters
'Kuchibeni' or 'Carnea' - pink flowers
'Honbeni' or 'Rosea'agm^[5] - pale rose flowers tipped purple, 18 inches long
'Issai Perfect' - light lavender flowers
'Jako' or 'Ivory Tower'
'Lawrence' - blue flowers, hardy cultivar
'Macrobotrys' or 'Longissima' - reddish-violet flower clusters one meter or longer
'Macrobotrys Cascade' - white and pinkish-purple flowers, vigorous grower
'Multijuga'agm^[6] - violet flowers with darker markings
'Nana Richins Purple' - purple flowers
'Nishiki' - variegated foliage
'Plena' or 'Violaceae Plena' - double blue flowers in dense clusters
'Praecox' or 'Domino' - purple flowers
'Purpurea' - unknown - May be Wisteria sinensis consequa which is sometimes labeled purpurea
'Royal Purple' - purple flowers
'Rubra'- unknown - may be Honbeni - sometimes labeled as Rubrum - deep pink to red flowers
'Texas Purple' - may be a sinensis or a hybrid, short racemes, purple flowers, produced while the plant is still young
'Violacea Plena' - double violet flowers, rosette-shaped
'White with Blue Eye' - also known as Sekines Blue - very fragrant