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Knotweeds

Fallopia/Polygonum spp.

Plant Description

Perennial with small green to white or pink flowers in drooping plume-like clusters from leaf axils, heart to spade shaped alternate leaves, hollow stems with nodes, and roots that grow 3-9 feet deep. Scientific names include: Fallopia japonica (Japanese knotweed), Fallopia x bohemica (Bohemian knotweed), Polygonum sachalinenses (Giant knotweed).

Plant Details

Life Forms
Habitats
ODA Listing
Soil and Moisture Conditions
Suggested Actions
Shade Preference
Mature Height 4-13'
Distribution Found through out Oregon with greatest concentration in western part of the state.
Control Mowing is not recommended. Contact your local watershed council, SWCD, or public works departments for assistance.
Disposal Methods All plant parts should be disposed of in sealed plastic bags because small fragments can start new infestations.
Reproduction and Spread Reproduce vegetatively via root, rhizome and stem fragments. Also in yards, vacant lots, park and field edges and other places.
Introduced Brought to North Maerica from Asia as an ornamental in the 1890s.
Look Alikes bamboo, other knotweeds
Impact Displaces native vegetation due to its aggressive growth. Creates bank erosion problems and is considered a potential flood hazard. Lowers quality of riparian habitat for fish and wildlife. Forms dense stands that crowd out all other vegetation, degrading native plant and animal habitat. Extremely vigorous rhizomes form deep, dense mat. Plants resprout from stem or root fragments creating new infestations downstream.
More Info
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