Japanese wisteria (Wisteria floribunda)

Synonyms: Glycine floribunda, Kraunhia floribunda, Rehsonia floribunda

Common Names: Fuji, noda-fuji

Description:

Japanese wisteria (Wisteria floribunda) is a woody, twining vine from Japan, in the pea family, long planted for its long, drooping clusters of fragrant purple flowers [1][3]. It escapes gardens and climbs over shrubs and trees, smothering and even toppling them, and it spreads across the ground by rooting runners [1][2]. MISIN tracks it because it forms dense, hard-to-remove thickets that crowd out native plants and damage forests [2].

Habit:

Japanese wisteria is a woody, deciduous vine that twines up and over supports, reaching 25 feet (8 m) or more, with stems that wrap in a clockwise direction [1]. Its leaves are alternate and pinnately compound (a row of leaflets along a central stalk), over 6 inches (15 cm) long, with about 15 to 19 leaflets each [1]. In spring, as the leaves come out, it produces long, drooping clusters (racemes) of pea-shaped purple to pink flowers, 12 to 18 inches (30 to 45 cm) long, that are very fragrant and open in sequence from the base of the cluster to the tip [1]. After flowering, it forms hanging, velvety (fuzzy) bean-like pods about 6 inches (15 cm) long that ripen in fall and may hang on into winter [1].

It is easiest to spot in spring, when the long, drooping purple flower clusters stand out on a climbing vine [1]. Later in the year, look for the big compound leaves, the twining woody stems, and the fuzzy hanging pods [1].

At-a-glance cues:

1. A woody vine with stems that twine clockwise up trees and supports [1]
2. Long (12?18 in), drooping clusters of fragrant purple, pea-shaped flowers in spring, opening base to tip [1]
3. Compound leaves with about 15?19 leaflets [1]
4. Hanging, velvety (fuzzy) bean-like pods about 6 inches long [1]

Leaves:

1. Arrangement: alternate, pinnately compound (leaflets in a row along a central stalk) [1]
2. Leaflets: about 15 to 19 per leaf [1]
3. Color: bright green [1]
4. Size: leaves over 6 inches (15 cm) long [1]

Stems:

1. Habit: a woody, deciduous, twining vine reaching 25 feet (8 m) or more along supports [1]
2. Twining direction: clockwise (Chinese wisteria twines counterclockwise) [1]
3. Runners: stems root where their nodes touch the ground, spreading the plant along the ground [1][2]

Flowers:

1. Color: purple to pink [1]
2. Shape: pea-shaped (typical of the pea family) [1]
3. Arrangement: in long, drooping clusters (racemes) 12 to 18 inches (30 to 45 cm) long, opening in sequence from the base to the tip [1]
4. Scent: very fragrant [1]
5. Bloom time: spring, as the leaves emerge [1]

Fruit and seeds:

1. Fruit: hanging, velvety (fuzzy) bean-like pods about 6 inches (15 cm) long [1]
2. Ripening: fall, sometimes hanging on into winter [1]
3. Spread: seeds from the pods (carried by water), plus rooting runners (stolons) that spread the plant along the ground [1][2]

Habitat:

Japanese wisteria is native to Japan [1][3]. It was brought to North America as an ornamental vine in the 1800s and has escaped cultivation, becoming invasive in the mid-Atlantic and southeastern United States [1].

It grows along forest edges, roadsides, and streams, and in disturbed woods, and it can invade a wide range of forest types and stages of growth [2].

Reproduction:

Japanese wisteria spreads in two ways [1][2]. It makes seeds inside velvety pods, and those seeds can be carried away by water to start new plants [1]. It also spreads on its own by runners (stolons) ? stems that run across the ground and root wherever their joints touch the soil, so a single plant can creep outward into a dense patch [1][2].

Because it spreads by both seed and runners, and resprouts after it is cut, removing it takes repeated effort [2]. Cut the climbing vines to stop them from strangling trees, then dig out and follow the rooting runners, and return to remove regrowth [2].

Impact and Damage:

For a homeowner, Japanese wisteria is a heavy, fast-growing vine that climbs and smothers shrubs and trees, and its runners root and spread it across a yard [1][2]. Its twining stems can wrap tightly around a trunk and girdle it, and the sheer weight of the vine can break branches [1].

In natural areas it climbs over and can topple large trees, opening gaps in the forest canopy that let even more wisteria in [2]. Its dense growth smothers and shades the native plants beneath it, and reduces the ability of trees and understory plants to grow back [2]. It forms dense thickets that are difficult to remove once established [1].

Similar species:

Japanese wisteria is most easily confused with the other wisterias ? the twining direction, the number of leaflets, and the flower pods are the best clues.

Chinese wisteria (Wisteria sinensis) is the other invasive Asian wisteria and looks very similar, but its stems twine counterclockwise (Japanese twines clockwise), it has fewer leaflets (about 7 to 13), and its flower clusters open all at once rather than in sequence from the base [1].

American wisteria (Wisteria frutescens) is a native wisteria of the southeastern United States, with smaller, more compact flower clusters and smooth (not velvety) seed pods, and it is far less aggressive [1][2].

Kentucky wisteria (Wisteria macrostachya) is another native wisteria, similar to American wisteria, with smooth pods and shorter flower clusters that bloom after the leaves are out.

Monitoring and rapid response:

Signs to watch for:

1. Long, drooping clusters of fragrant purple flowers on a climbing woody vine in spring, along forest edges, roadsides, and streams [1][2]
2. Woody stems twining clockwise up trees, and runners rooting along the ground [1]
3. Hanging, fuzzy bean-like pods later in the year [1]

What you can do:

1. Cut the climbing vines near the ground to stop them from strangling trees and shrubs [2].
2. Dig or pull up seedlings, small plants, and the rooting runners when the soil is moist, following the runners out and getting the roots [1][2].
3. Expect the plant to resprout after cutting ? plan to return and remove the regrowth over more than one season [2].
4. Cut off and bag the seed pods before they open, so seeds can't spread [1].
5. Natural-area crews should cut vines off valuable trees first, then work outward, removing small outlying plants and rooting runners across the site over repeat visits [2].

When to call a professional:

1. Large, well-established vines high in the tree canopy, or thickets that keep resprouting from the roots after cutting [2]
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. NC State Extension. Wisteria floribunda (Japanese Wisteria). plants.ces.ncsu.edu
2. Wisconsin Department of Natural Resources. Japanese Wisteria; Chinese Wisteria (Wisteria floribunda; Wisteria sinensis). dnr.wisconsin.gov
3. Plants of the World Online (Kew). Wisteria floribunda (Willd.) DC. powo.science.kew.org

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