Jepson eFlora: Taxon page
Key to families | Table of families and genera
Previous taxon Index to accepted names and synonyms:
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
Next taxon
Polygonum majus
WIRY 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
Genus: PolygonumView DescriptionDichotomous Key

Common Name: KNOTWEED
Habit: Annual, perennial herb to shrub. Stem: prostrate to erect, 8--16-ribbed or 4--5-angled with ribs 0 or obscure; glabrous or papillate-scabrous. Leaf: cauline, alternate, petioled or not; ocrea generally jointed to leaf, generally cylindric proximally, generally translucent distally, white or silvery, 2-lobed, glabrous, disintegrating to fibers or completely; blade linear, lanceolate, elliptic, ovate, or subround, entire. Inflorescence: axillary, terminal, generally spike-like; peduncle 0; pedicels present or 0, included in to exserted from bractlets; flowers 1--7(10). Flower: bisexual, base not stalk-like; perianth not enlarging, bell- to urn-shaped, glabrous, white or green-white to pink; perianth parts 5, fused 3--60[70]%, petal- or sepal-like, similar [or not], outer +- keeled or not, < to > inner, midveins generally a different shade or color than rest of perianth; stamens 3--8 (some staminodes or not), filaments or at least innermost free, wider at base, fused to perianth tube or not, anthers elliptic to oblong, white-yellow or generally pink to purple (orange-pink); styles (2)3, generally spreading, free or fused basally, stigmas 2--3, head-like. Fruit: included or exserted, wings 0, angles (2)3, 1 face much narrower than other (1)2 or not; tip beak-like, yellow-green, brown, or black. Seed: embryo curved.
Species In Genus: +- 65 species: +- worldwide; sect. Duravia restricted to western North America. Etymology: (Greek: poly, many, gony, knee joint, or gone, seed, of uncertain meaning) Note: Many species of sect. Polygonum with 2 kinds of fruit, differing in germination and morphology (summer fruit brown, ovate, tubercled to smooth; late-season fruit olive-green, lanceolate, smooth, 2--5 × > summer), but of little taxonomic importance. Mature, early-season plants with leaves, flowers, fruits needed for identification. Flowers "closed" or "1/2-open" should be determined on herbarium specimens. Other taxa in TJM (1993) moved to Aconogonon, Bistorta, Fallopia, Persicaria.

Polygonum majus (Meisn.) Piper
NATIVE
Habit: Annual. Stem: erect, 15--60 cm, +- wiry, generally papillate-scabrous, green, +- angled, branches 0 or not. Leaf: basal leaves often early-deciduous; ocreae 5--12 mm, glabrous or papillate-scabrous, proximally cylindric, distally torn or disintegrating to fibers; petiole 0--2 mm; blade 15--70 mm, 2--8 mm wide, lance-linear to narrowly oblong or lanceolate, margin rolled under, papillate-fine-dentate, tip acute or mucronate. Inflorescence: axillary, terminal, spike-like; pedicels exserted, reflexed, 0.5--1 mm; flowers 2--5. Flower: open or 1/2-open; perianth (3.5)4--5 mm, white or pink, tube 9--17% of length, lobes overlapped, oblong to oblong-obovate, +- keeled in distal 1/4, tips rounded, hood-shaped, midvein branches 0 or short; stamens 8. Fruit: included, 3.5--5 mm, elliptic, black, shiny or dull, smooth to striate-tubercled.
Ecology: Dry plains, meadows, serpentine or not; Elevation: 500--2000 m. Bioregional Distribution: KR, NCoR, CaR, SN, SnBr, w MP; Distribution Outside California: to British Columbia, Idaho. Flowering Time: Jun--Sep
Synonyms: Polygonum douglasii subsp. majus (Meisn.) J.C. Hickman
eFlora Treatment Author: Mihai Costea
Jepson Online Interchange

Previous taxon: Polygonum hickmanii
Next taxon: Polygonum marinense

Name Search
botanical illustration including Polygonum majus

Contact/Feedback

Citation for this treatment: Mihai Costea 2016. Polygonum majus, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=39209, accessed on December 04, 2016.

Citation for the whole project: Jepson Flora Project (eds.) 2016. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on December 04, 2016.


Polygonum majus
click for enlargement
© 2008 Keir Morse
Polygonum majus
click for enlargement
© 2008 Keir Morse
Polygonum majus
click for enlargement
© 2008 Keir Morse
Polygonum majus
click for enlargement
© 2008 Keir Morse
Polygonum majus
click for enlargement
© 2009 Neal Kramer
Polygonum majus
click for enlargement
© 2009 Neal Kramer

More photos of Polygonum majus in CalPhotos


Geographic subdivisions for Polygonum majus:
KR, NCoR, CaR, SN, SnBr, w MP;
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
READ ABOUT YELLOW FLAGS
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).

View elevation by latitude chart
Data provided by the participants of the Consortium of California Herbaria.
View all CCH records

CCH collections by month

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