NATIVE
RANGE
China and Japan
DESCRIPTION
Chinese and Japanese wisteria
are exotic, showy, woody ornamental vines. These vigorous vines can
climb trees, apparently limited only by the height of the tree, and have
been observed to reach 65 feet. Unlike American wisteria (Wisteria
frutescens), native to the southeastern U.S., which flowers June through
August, and produces a non-hairy seed pod 2-4 inches long, both exotic wisterias
flower in the springtime (April-May) and produce a velvety seed pod. The
fuzzy brown seed pods are 4-6 inches long, narrowed toward the base, with
constrictions between the seeds. Stems of the exotic wisterias can
grow to 15 inches in diameter in older plants. White-barked Japanese wisteria
vines twine clockwise around the host plant and Chinese wisteria twines counter-clockwise.
The compound leaves, consisting of 7-13 (Chinese) or 13-19 (Japanese)
smaller leaf units, called leaflets, are about 1 foot long and alternate
along the stem. Fragrant, violet to blue-violet flowers, ½ to
1 inch long, occur in showy, pendulous clusters that hang gracefully from
the twining stems.
ECOLOGICAL THREAT
Exotic wisterias impair
and overtake native shrubs and trees through strangling or shading. Climbing
wisteria vines can kill sizable trees, opening the forest canopy and increasing
sunlight to the forest floor, which in turn favors its aggressive growth. Chinese
and Japanese wisterias are hardy and aggressive, capable of forming thickets
so dense that little else grows.
DISTRIBUTION
IN THE UNITED STATES
Japanese and Chinese wisteria are found extensively
throughout the eastern states.
HABITAT IN THE UNITED STATES
The ideal
habitat for exotic wisterias is in full sun, but established vines will persist
and reproduce in partial shade. Vines often climb surrounding vegetation
and structures toward sunlight. Wisteria tolerates a variety of soil
and moisture regimes but prefers loamy, deep, well drained soils. Infestations
are commonly found along forest edges, roadsides, ditches, and rights-of-way.
BACKGROUND
Chinese
wisteria was brought to the U.S. from China in 1816 and Japanese wisteria
was introduced from Japan around 1830. Both were brought in as ornamentals. They
have been grown extensively in the southern U.S. as decorative additions
to porches, gazebos, walls, and gardens. Most infestations in natural
areas are a result of escapes from landscape plantings.
BIOLOGY & SPREAD
Exotic wisterias
are long-lived, some vines surviving 50 years or more. Vegetative reproduction
is their primary means of expansion. Numerous stolons, or above-ground
stems, develop roots and shoots at short intervals. Abundant seeds
may also be produced if conditions are favorable, but flower buds are susceptible
to winter kill. In riparian habitats, seeds may be carried downstream
in water for great distances.
MANAGEMENT OPTIONS
The only practical
methods currently available for control of exotic wisterias are mechanical
and chemical. Cut climbing or trailing vines as close to the root collar
as possible. This technique, while labor intensive, is feasible for
small populations, as a pretreatment for large impenetrable infestations,
or for areas where herbicide use is not desirable. Wisteria will continue
to resprout after cutting until its root stores are exhausted. For
this reason, cutting should begin early in the growing season and, if possible,
sprouts cut every few weeks until autumn. Cutting will stop the growth
of existing vines and and prevent seed production. However, cut vines
left coiled around trunks may eventually girdle trees and shrubs as they
continue to grow and increase in girth. For this reason, the vines
should be removed entirely or at least cut periodically along their length.
Manual
Grubbing, removal of entire plants
from the roots up, is appropriate for small initial populations or environmentally
sensitive areas where herbicides cannot be used. Using a pulaski, weed wrench
or similar digging tool, remove the entire plant, including all roots and
runners. Juvenile plants can be hand pulled depending on soil conditions
and root development. Any portions of the root system not removed may
resprout. All plant parts (including mature fruit) should be bagged and disposed
of in a trash dumpster to prevent reestablishment.
Chemical
Cut stump application
Cut stump treatment, using a systemic herbicide,
is effective in areas where vines are established within or around desirable
native plants or where they have grown into the canopy. This treatment is
effective as long as the ground is not frozen. Cut the stem as close to ground
level as possible. Immediately apply a 25% solution of glyphosate (e.g.,
Roundup®) or triclopyr (e.g., Garlon) and water to the cross section of the
stem. Retreatment with a foliar application of glyphosate may be necessary
for any sprouts.
Foliar application
Use foliar spray herbicide
treatments to control large infestations of exotic wisterias. It may be necessary
to precede foliar applications with stump treatments to reduce the risk of
damaging non-target species. Apply a 2% concentration of glyphosate
(e.g. Roundup®) or triclopyr (e.g. Garlon) and water, plus a 0.5% non-ionic
surfactant to thoroughly wet all foliage. Chlorpyralid (e.g. Transline) is
effective at a concentration of 0.5% and is selective to plants in the aster,
buckwheat, and pea families. Caution should be taken with chlorpyralid as
groundwater pollution through leaching can be a problem with certain soil
types. Do not apply spray so heavily that herbicide drips off the leaves.
Glyphosate is a non-selective systemic herbicide that may kill non-target
plants that are only partially contacted by spray. Triclopyr is selective
to broadleaved species and is a better choice if native grasses are present.
Ambient air temperature should be above 65ºF for all foliar treatments.
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
CONTACTS
For more information on
the management of exotic wisterias, please contact:
- Kris Johnson, Great Smoky Mountains
National Park, Gatlinburg, TN
SUGGESTED ALTERNATIVE PLANTS
There are
a variety of creeping or climbing vines native to the eastern U.S. that are good
alternatives to the invasive exotic wisterias. Some examples include American
wisteria (Wisteria frutescens), trumpet
creeper (Campsis radicans), trumpet honeysuckle (Lonicera sempervirens),
Dutchman’s pipe (Aristolochia macrophylla), and crossvine (Bignonia
capreolata). Contact your local native plant society for information
on sources of these and other native plants.
OTHER LINKS
AUTHOR
Tom Remaley, Great Smoky Mountains National
Park, Gatlinburg, TN
EDITOR
Jil M. Swearingen, National Park Service,
Washington, DC
NCR-EPMT, National Park Service, Washington, DC
PHOTOGRAPHS
Susan Ross, Great Smoky Mountains National Park,
Gatlinburg, TN
REFERENCES
Dirr, Michael A. 1990. Manual of
Woody Landscape Plants: Their Identification, Ornamental Characteristics,
Culture, Propagation and Uses. Stipes Publishing Co., Champaign, IL.
Pp. 926-929.
Gleason, H.A., A. Cronquist. 1991.
Manual of vascular plants of northeastern United States and adjacent Canada.
2nd ed. The New York Botanical Garden, 910.
Isely, D. 1990. Vascular flora of
the southeastern United States. Volume 3, Part 2 Leguminosae. Chapel Hill,
NC: The University of North Carolina Press, 96.
Radford, A.E., H.E. Ahles, C.R.
Bell. 1968. Manual of vascular flora of the Carolinas. Chapel Hill, NC: The
University of North Carolina Press, p. 1183.
Rehder, A. 1993. Manual of cultivated
trees and shrubs. Vol. 1. Dioscorides Press, Portland OR. p.507.
Thomas, L.K. Jr. 1993. Chemical
grubbing for control of exotic wisteria. Castanea, 58(3):209-213.
Plant Conservation
Alliance, Alien Plant Working Group.
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