Fallopia japonica/NJ

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Caryophyllanae
Order	Caryophyllales
Family	Polygonaceae
Genus	Reynoutria

Scientific Name

Reynoutria japonica

Scientific Name Synonyms

Fallopia japonica

Polygonum cuspidatum

Fallopia japonica var. japonica

Common Name

Japanese knotweed

Common Name: Japanese knotweed, fleeceflower; Japanese bamboo, Fallopia japonica
Family Name: Polygonaceae - Knotweed family
Native Range: Eastern Asia
NJ Status: Widespread and highly threatening to native communities.

General Description

• Herbaceous perennial reaching 3 - 10’ in height.
• Stems hollow, jointed, green to reddish-green in color.
• Shoots grow from spreading rhizomes.
• Small rhizome fragments can sprout new plants.
• Flooding, excavations, and roadwork spread this plant.
• Though killed by frost, stems can persist through winter.

Leaves

• Alternate, toothless, broadly oval with pointed tips
• From 3 - 6” long and 2 - 5” wide.

Flowers

• Small, greenish-white, borne on branched stems emerging from upper leaf axils.
• 3 - 6” long
• Bloom from August to September.

Fruit

• Black, smooth, shiny
• 3-angled seeds contained in a papery, winged fruit.
• Ripening in September.

Habitat

• Stream side, open forest, forest edge, wet meadow, roadside, yard, garden

Commercially Available

No

Look-alikes

giant knotweed (Polygonum sachalinense)

• Invasive that grows to over 12’ tall
• Leaves often over 12’ long
• Less showy flowers than Japanese knotweed

Bohemian knotweed (Polygonum x bohemicum)

• Invasive perennial, hybrid between giant and Japanese knotweed
• No known populations in NJ
• Leaves oval to heart-shaped
• Flowers about the same length as leaves
• Prefers moist areas

Control Recommendations

Foliar Spray: FS-2

• Glyphosate 3.00%
• Please see our Herbicide Use Suggestions and Mixing Guide for more information
• Mowing is recommended only as pre-treatment to weaken root system (Mow in June, apply foliar spray in September)
• September application is recommended
• Stem injection using glyphosate is highly effective but very time consuming for moderate to large populations (see http://stopknotweednj.com/knotweed_eradication.htm)
• As necessary, seek aquatic application permit and use wetlands-appropriate herbicides and surfactants.

List of Resources

• National Park Service
• USDA PLANTS
• BugwoodWiki