| USDA PLANTS Symbol: FAJA2 U.S. Nativity: Exotic Habit: Forbs/Herbs Vines |
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| Fallopia japonica (Houttuyn) Ronse-Decraene |
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Taxonomic Rank: Magnoliopsida: Polygonales: Polygonaceae |
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Japanese knotweed is a dense growing shrub reaching heights of 10 ft. (3 m). The semi-woody stem is hollow with enlarged nodes. Leaves are alternate, 6 in. (15.2 cm) long, 3-4 in. (7.6-10 cm) wide and broadly-ovate. Flowering occurs in late summer, when small, greenish-white flowers develop in long panicles in the axils of the leaves. Plants are dioecious (male and female flowers occur on separate plants). Japanese knotweed commonly invades disturbed areas with high light, such as roadsides and stream banks. Reproduction occurs both vegetatively (rhizomes) and seeds, making this plant extremely hard to eradicate. The dense patches shade and displace other plant life and reduce wildlife habitat. Japanese knotweed resembles giant knotweed (Polygonum sachalinense), but giant knotweed is larger and has heart-shaped leaves. Japanese knotweed is native to eastern Asia and was first introduced into North America in the late 1800s. |
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Identification, Biology, Control and Management Resources
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| EDDMapS Distribution: This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org |
 State List This map identifies those states that list this species on their invasive species list or law. 
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| Invasive Listing Sources: |
