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Japanese Knotweed

Reynoutria japonica

—
Not native

Not native to Alabama. How scores work Is it native here?

Profile 65%

Height
10–13 feet
Spread
3–20 feet
Light
Full sun
Soil moisture
Usually moist

At a glance

Life cycle
Perennial

Not yet recorded · Leaves · Bloom

This plant is missing most of its facts, so Quercus is looking them up in old botany books.

Recorded in 10 Alabama counties.

Ecological relationships

Who uses this plant?

What these records mean

43CaterpillarsGenus host records with ranges including AL

Genus host records with ranges including AL · Polygonum

  • Achyra rantalisGarden Webworm Moth
  • Acronicta insularisHenry's Marsh Moth, Cattail Caterpillar
  • Acronicta oblinitaSmeared Dagger
  • Anticlea multiferataMany-Lined Carpet
  • Apantesis argeArge Tiger Moth
  • Apantesis naisNais Tiger Moth
  • Archips semiferanusOak Leafroller Moth
  • Calothysanis amaturariaCross-Lined Wave
  • Chionodes discoocellellaEyeringed Chionodes
  • Coleophora cratipennellaStreaked Coleophora
Show all 43
  • Costaconvexa centrostrigariaBent-Lined Carpet
  • Dypterygia rozmaniAmerican Bird's-Wing
  • Elophila icciusalisPondside Pyralid, Pondside Crambid
  • Elophila obliteralisWaterlily Leafcutter Moth
  • Emmelina monodactylaMorning-Glory Plume Moth
  • Epiblema otiosanaBidens Borer Moth
  • Eusarca confusariaConfused Eusarca
  • Feltia subterraneaSubterranean Dart, Granulate Cutworm
  • Haematopis gratariaChickweed Geometer
  • Helicoverpa zeaCorn Earworm Moth
  • Homophoberia apicosaBlack Wedge-Spot, Smartweed Groundling
  • Hyles lineataWhite-Lined Sphinx
  • Hypena scabraGreen Cloverworm Bomolocha, Black Snout
  • Maliattha synochitisBlack-Dotted Lithacodia, Black-Dotted Glyph, Brass-Dotted Grass Moth
  • Melanolophia canadariaCanadian Melanolphia, Variable Redmarked Looper
  • Metarranthis duariaRuddy Metarranthis
  • Nephelodes miniansBronzed Cutworm
  • Nomophila nearcticaLucerne Moth, American Celery Webworm
  • Orthonama obstipataThe Gem
  • Ostrinia obumbratalisSmartweed Borer
  • Ostrinia penitalisAmerican Lotus Borer, Lily Moth
  • Parapoynx obscuralisObscure Pondweed Moth
  • Patania silicalisHerbivorous Patania, Herbivorous Pleuroptya
  • Prochoerodes lineolaLarge Maple Spanworm Moth
  • Pseudeustrotia carneolaPink-Barred Lithacodia, Pink-Barred Pseudeustrotia
  • Saucrobotys futilalisDogbane Saucrobotys
  • Schinia scissoidesDivided Flower Moth
  • Schinia spinosaeSpinose Flower Moth
  • Scopula limboundataLarge Lace-Border
  • Spilosoma congruaAgreeable Tiger Moth
  • Spilosoma virginicaVirginian Tiger Moth, Yellow Woolybear Moth, Yellow Bear
  • Strymon melinusGray Hairstreak
  • Aroga alleriella
Shropshire & Tallamy 2025, Lepidoptera of North America north of Mexico, ZooKeys 1261 (ODbL)
—BeesSoutheastern regional records
—Specialist beesPollen specialists
58BirdsRecorded genus food-resource interactions; not a state feeding claim

Recorded genus food-resource interactions; not a state feeding claim · Polygonum

  • Agelaius phoeniceusRed-winged Blackbird
  • Aix sponsaWood Duck
  • Alectoris chukarChukar
  • Anas acutaNorthern Pintail
  • Anas creccaGreen-winged Teal
  • Anas platyrhynchosMallard
  • Anser albifronsGreater White-fronted Goose
  • Anthus rubescensAmerican Pipit
  • Aythya affinisLesser Scaup
  • Aythya americanaRedhead
Show all 58
  • Aythya collarisRing-necked Duck
  • Aythya valisineriaCanvasback
  • Bonasa umbellusRuffed Grouse
  • Bucephala clangulaCommon Goldeneye
  • Callipepla californicaCalifornia Quail
  • Centrocercus urophasianusGreater Sage-Grouse
  • Colinus virginianusNorthern Bobwhite
  • Columba liviaRock Pigeon
  • Columbina passerinaCommon Ground Dove
  • Coturnicops noveboracensisYellow Rail
  • Dendragapus obscurusDusky Grouse
  • Dendrocygna autumnalisBlack-bellied Whistling-Duck
  • Dolichonyx oryzivorusBobolink
  • Eremophila alpestrisHorned Lark
  • Euphagus cyanocephalusBrewer's Blackbird
  • Francolinus francolinusBlack Francolin
  • Fulica americanaAmerican Coot
  • Gallinula galeataCommon Gallinule
  • Haemorhous mexicanusHouse Finch
  • Junco hyemalisDark-eyed Junco
  • Lagopus lagopusWillow Ptarmigan
  • Mareca americanaAmerican Wigeon
  • Meleagris gallopavoWild Turkey
  • Melospiza melodiaSong Sparrow
  • Melozone crissalisCalifornia Towhee
  • Molothrus aterBrown-headed Cowbird
  • Oreortyx pictusMountain Quail
  • Oxyura jamaicensisRuddy Duck
  • Passer domesticusHouse Sparrow
  • Perdix perdixGray Partridge
  • Pheucticus melanocephalusBlack-headed Grosbeak
  • Pinicola enucleatorPine Grosbeak
  • Pipilo maculatusSpotted Towhee
  • Porzana carolinaSora
  • Quiscalus quisculaCommon Grackle
  • Rallus elegansKing Rail
  • Rallus limicolaVirginia Rail
  • Sialia mexicanaWestern Bluebird
  • Sialia sialisEastern Bluebird
  • Spinus psaltriaLesser Goldfinch
  • Spizella passerinaChipping Sparrow
  • Sturnus vulgarisEuropean Starling
  • Turdus migratoriusAmerican Robin
  • Tympanuchus phasianellusSharp-tailed Grouse
  • Vireo griseusWhite-eyed Vireo
  • Zenaida macrouraMourning Dove
  • Zonotrichia atricapillaGolden-crowned Sparrow
  • Zonotrichia leucophrysWhite-crowned Sparrow
Hurlbert, Olsen, Sawyer & Winner 2021, Avian Diet Database, Scientific Data 8: 260 (CC0)

Direct food only: birds recorded eating this genus across North America. Caterpillars on host plants also feed nesting birds. NC Native Plant Society: butterfly gardening

Growing and identification

Plant details

Family
Polygonaceae
Flower color
Cream, green or white

What its natural habitat tells you

Safety has not been reviewed for this plant; check toxicity and thorns before planting.

Growing sources and scope
Also known as

Polygonum cuspidatum; knotweed

Conservation status

Alabama rankSNA
Global rankGNR
AL statusNot verified
Federal statusNot verified

Conservation source Global and federal source

Native alternatives

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Sources