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Fallopia japonica
JAPANESE KNOTWEED

Higher Taxonomy
Family: PolygonaceaeView DescriptionDichotomous Key

Common Name: BUCKWHEAT FAMILY
Habit: Annual to shrub [tree]. Stem: nodes swollen or not. Leaf: simple, basal or cauline, generally alternate; ocreae present or 0, generally scarious, persistent or not. Inflorescence: flower clusters in axillary to terminal cyme-, panicle-, raceme-, spike-, umbel- or head-like arrangements, entire inflorescence or main inflorescence branches generally subtended by bracts ("inflorescence bracts"); peduncles present or 0; flower clusters in Eriogoneae-Eriogonoideae subtended by involucre of >= 1 free or +- fused, sometimes awn-tipped bracts ("involucre bracts") or, in Polygonoideae and rarely in Eriogonoideae, not (if bracts completely fused, involucre "tubular"); pedicels in Eriogoneae each often subtended by 2 free, transparent, linear bractlets or in Polygonoideae all subtended by 2+ fused, membranous, wide bractlets. Flower: generally bisexual, small, 1--200 per node; perianth parts 2--6, generally in 2 whorls, free or basally fused, generally petal-like, often +- concave adaxially, often darker at midvein, often turning +- red or +- brown in age; stamens [1]3 or 6--9 in 2 whorls; ovary superior, 1-chambered, ovule 1, styles 1--3. Fruit: achenes, included in or exserted from perianth, generally 3-angled, ovoid or elliptic, generally glabrous.
Genera In Family: 48 genera, +- 1200 species: worldwide, especially northern temperate; some cultivated for food (Coccoloba, sea-grape; Fagopyrum, Rheum, Rumex) or ornamental (Antigonon, lovechain; Coccoloba; Muehlenbeckia; Persicaria; Polygonum), a few timbered (Coccoloba; Triplaris). Several (Emex; Fallopia; Persicaria; Polygonum; Rumex) are weeds. Note: Treatment of genera in Eriogonoideae based on monographic work of James L. Reveal. Involucre number throughout is number (1--many) per ultimate grouping, at tips of ultimate branches; flower number is per flower cluster or involucre, unless otherwise stated. Fagopyrum esculentum Moench not naturalized, considered an historical waif (or garden weed +- presently), therefore not treated.
eFlora Treatment Author: Mihai Costea, except as noted
Scientific Editor: Thomas J. Rosatti, Bruce G. Baldwin.
Genus: FallopiaView DescriptionDichotomous Key

Habit: Annual, perennial herb, vine or not. Stem: erect, trailing, or twining, glabrous or hairy, ribs 0. Leaf: cauline, alternate, petioled; ocrea persistent or not, cylindric, papery, opaque; blade broad-ovate to triangular, entire. Inflorescence: axillary, terminal, spike-, panicle-, or raceme-like; flowers 3--7; peduncle present or 0. Flower: bisexual or pistillate (1 kind per pl); perianth generally enlarging, bell-shaped, pale green or white to pink, glabrous, base stalk-like, parts 5, fused basally or +- completely, of 2 kinds, outer 3 generally winged, > inner 2; stamens 6--8, filaments free, wider basally, glabrous or hairy, anthers yellow to pink or red, ovate to elliptic; styles 3, spreading, fused basally or +- completely, stigmas head-like, fringed, or peltate. Fruit: included or exserted, 3-angled, brown to black. Seed: embryo straight.
Species In Genus: 12 species: America, Europe, Asia, Africa. Etymology: (for Gabriele Fallopio, 1523--1562, Italian professor of anatomy, botany, and surgery, for whom Fallopian tubes also named)

Fallopia japonica (Houtt.) Ronse Decr.
NATURALIZED
Habit: Perennial herb, rhizomed. Stem: generally in dense clumps, erect, generally 1--2 m, glaucous, glabrous, branches few. Leaf: ocrea 5--8 mm, +- brown, margin oblique, glabrous or puberulent; blade 6--13 cm, 5--10 cm wide, widely ovate, abaxially with 1-celled hairs < 0.1 mm on veins, adaxially glabrous, base truncate, tip acuminate. Inflorescence: axillary, generally distal, erect or spreading, panicle-like, 3--10 cm; peduncle 0--2.5 cm; pedicels 3--5 mm, glabrous; flowers 4--6. Flower: bisexual or functionally +- unisexual; perianth 4.5--6.5 mm, winged, +- white, glabrous, lobes obovate to elliptic, tips obtuse to acute; stamens 6--8, filaments glabrous; styles fused basally, stigmas fringed. Fruit: included, 3.8--5 mm, 2--2.2 mm wide, dark-brown, shiny, smooth. Chromosomes: 2n=44,88.
Ecology: Disturbed places; Elevation: < 1000 m. Bioregional Distribution: n CA-FP (esp s NCoR), SnFrB; Distribution Outside California: to eastern North America; native to Japan. Flowering Time: Aug--Oct Note: Introduced as ornamental, spreading aggressively.
Synonyms: Reynoutria japonica Houtt.; Polygonum cuspidatum Siebold & Zucc.; Tiniaria japonica (Houtt.) Hedberg
eFlora Treatment Author: Mihai Costea
Jepson Online Interchange
Noxious Weed

Previous taxon: Fallopia convolvulus
Next taxon: Fallopia sachalinensis

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botanical illustration including Fallopia japonica

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Citation for this treatment: Mihai Costea 2016. Fallopia japonica, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=82464, accessed on February 14, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on February 14, 2016.


Geographic subdivisions for Fallopia japonica:
n CA-FP (esp s NCoR), SnFrB;
Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.