Native & Naturalized Plants of the Carolinas & Georgia


1122

Forb
Perennial
Monoecious or dioecious

Non-native: East Asia
Documented growing wild in GA NC SC

Uncommon in GA-NC-SC

Look for it on roadsides, disturbed areas, riverbanks and sandbars, often forming dense thickets, per Weakley's Flora

map
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INVASIVE

This plant is causing problems in natural areas outside its native range, according to authorities such as:

Alabama Invasive Plant Council, 2012
Brooklyn Botanic Garden
Georgia Exotic Pest Plant Council, 2006
Kentucky Exotic Pest Plant Council, 2013
NC Department of Transportation
SC Exotic Pest Plant Council, 2014
Tennessee Exotic Pest Plant Council, 2009
US Fish & Wildlife Service
US Forest Service Southern Research Station
Virginia Department of Conservation and Recreation, 2014

 

LEAVES:
Simple
Alternate

FLOWER:
Spring/Summer/Fall
Calyx white (rarely tinged with pink)
Functionally unisexual
5-parted calyx
Petals absent
8 stamens
Superior ovary
Flowers in axillary paniculate racemes

FRUIT:
Summer/Fall
Brown, lustrous
Nutlet

 

TO LEARN MORE about this plant, look it up in a good book!



Spermatophytes (seed plants): Angiosperms (flowering plants): Eudicots: Core Eudicots: Caryophyllales

WEAKLEY'S FLORA (11/30/12):
Reynoutria japonica   FAMILY Polygonaceae

SYNONYMOUS WITH PLANTS NATIONAL DATABASE:
Polygonum cuspidatum   FAMILY Polygonaceae

SYNONYMOUS WITH VASCULAR FLORA OF THE CAROLINAS (1968) 063-04-023:
Polygonum cuspidatum   FAMILY Polygonaceae

SYNONYMOUS WITH Generic Limits in Polygonum (Ronse Decraene & Akeroyd, 1988)
Fallopia japonica

SYNONYMOUS WITH Manual of the Southeastern Flora (Small, 1933)
Pleuropterus zuccarinii

 

COMMON NAME:
Japanese Knotweed


Click or hover over the thumbnails to see larger pictures.

image of Reynoutria japonica

USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913    pnd_plzu_001_lvd

        

image of Reynoutria japonica

JK Marlow    jkm160322_058

March    Greenville County    SC

Riparian zone along urban waterway

Stems erect, stout, striate, papillate, often with red or purple spots, per Flora of China.

image of Reynoutria japonica

JK Marlow    jkm160322_059

March    Greenville County    SC

Riparian zone along urban waterway

Ocrea oblique, per Flora of China.

image of Reynoutria japonica

JK Marlow    jkm160331_184

March    Greenville County    SC

Riparian zone along urban waterway

image of Reynoutria japonica

JK Marlow    s050406_a

April    Greenville County    SC

Roadside

Mid-branch leaves truncate (to very broadly V-shaped), per Weakley's Flora.

image of Reynoutria japonica

JK Marlow    jkm130628_308

June    Cherokee County    NC

Murphy River Walk

image of Reynoutria japonica

JK Marlow    jkm0407a_37

July    Greenville County    SC

Mortgage lenders in the UK may refuse to loan on property with Japanese Knotweed

image of Reynoutria japonica

JK Marlow    jkm0407b_08

July    Greenville County    SC

Roadside

image of Reynoutria japonica

JK Marlow    jkm0407b_13

July    Greenville County    SC

Roadside

Flowers in axillary, paniculate racemes. Calyx 1.5-2mm long in flower, per Vascular Flora of the Carolinas.

image of Reynoutria japonica

JK Marlow    s080705_a

July    Swain County    NC

Veins of leaf underside minutely scabrous with scattered bumps, per Weakley's Flora.

image of Reynoutria japonica

JK Marlow    jkm160818_631

August    Polk County    NC

Pearson's Falls

image of Reynoutria japonica

JK Marlow    jkm160818_632

August    Polk County    NC

Pearson's Falls