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Polygonum aviculare subsp. depressum

Higher Taxonomy
Family: PolygonaceaeView DescriptionDichotomous Key

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: 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.
eFlora Treatment Author: Mihai Costea
Species: Polygonum aviculareView Description 

Habit: Annual. Stem: prostrate to erect, 5--200 cm, glabrous, green, ribbed, branched. Leaf: distal > distal flowers; ocreae 3--15 mm, distally disintegrating to fibers or +- completely persistent; petiole 0.3--9 mm; blade 6--50(60) mm, 0.5--22 mm wide, narrowly elliptic, lanceolate, elliptic, or obovate, green to gray-green, margin flat, tip acute or rounded. Inflorescence: axillary; flowers 1--6(8), crowded distally or not; pedicels included to exserted, 1.5--5 mm. Flower: closed or half-open; perianth 1.8--5.5 mm, generally not pouched at base, +- green, margin white to red, tube 20--57% of length, lobes overlapped or not, not keeled, oblong to obovate, tip rounded, generally hood-shaped, midvein branched or not; stamens 5--8. Fruit: included or exserted, 1.2--4.2 mm, ovate, light- to dark-brown, dull, (2)3--angled, faces +- unequal, generally coarsely striate-tubercled; late-season common or not, 2--5 mm. Chromosomes: 2n=40,60.
Note: Taxonomically controversial, generally self-pollinated, self-fertilized, polyploid complex in which varieties to species have been named, but intergradation precludes recognition as species.

Polygonum aviculare subsp. depressum (Meisn.) Arcang.
Habit: Annual, short-lived perennial herb, generally mat-forming. Stem: 3--15, prostrate to ascending, (5)10--50(100) cm, branches many. Leaf: stem leaves 1--2.3(3.4) × > branch leaves; ocreae either 3--5.5 mm, distally soon disintegrating +- completely, or 7--12 mm, distally membranous, +- torn on margins, overlapped on distal stems; petiole 0.5--3 mm; blade (6.2)8--27(35) mm, (1.4)2--7(10) mm wide, elliptic to narrowly elliptic or oblanceolate, 2.8--5.7(6.5) × as long as wide, (longitudinally striate), tip obtuse or acute. Inflorescence: pedicels included, 1--2.5 mm flowers; 2--7, crowded distally or not. Flower: perianth (1.8)2--3.4(4) mm, green or red-brown, margins white, tube 40--57% of length, lobes overlapped, +- spreading in fruit, oblong, flat, or obscurely hood-shaped in fruit, midveins unbranched, thin to thickened; stamens 5--7. Fruit: +- exserted, 1.5--2.7(3) mm, ovate, dark-brown, (2)3-angled, 1 face +- narrower, tip straight or +- bent toward +- narrow face, generally striate-tubercled; late-season common, 2.5--4.5 mm. Chromosomes: 2n=40,60.
Ecology: Disturbed places; Elevation: < 2000 m. Bioregional Distribution: CA; Distribution Outside California: worldwide. Flowering Time: May--Nov Note: More trample-resistant than Polygonum aviculare subsp. aviculare; Polygonum montereyense Brenckle +- distinctive (ocreae 8--12 mm, especially silvery, persistent) may deserve infraspecific recognition but further study needed.
Synonyms: Polygonum aequale Lindm.; Polygonum arenastrum Boreau; Polygonum calcatum Lindm.; Polygonum microspermum Boreau
eFlora Treatment Author: Mihai Costea
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botanical illustration including Polygonum aviculare subsp. depressum


Citation for this treatment: Mihai Costea 2017. Polygonum aviculare subsp. depressum, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on April 28, 2017.

Citation for the whole project: Jepson Flora Project (eds.) 2017. Jepson eFlora,, accessed on April 28, 2017.

Geographic subdivisions for Polygonum aviculare subsp. depressum:
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.
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.