Polygonum aviculare |
Polygonum tenue |
|||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
birdweed, common knotgrass, common knotweed, doorweed, dooryard knotweed, knotgrass, knotweed, lowgrass, pigweed, prostrate knotweed, renouée des oiseaux, yard knotweed |
pleat-leaf knotweed, slender knotweed |
|||||||||||||||||||||||||||||
Habit | Plants green or bluish green, green after drying, sometimes whitish from powdery mildew, homophyllous or heterophyllous. | Herbs. | ||||||||||||||||||||||||||||
Stems | prostrate to erect, branched, flexuous, 5–200 cm. |
erect, green or brown-ish, simple or branched from below middle, not wiry, 5–50 cm, glabrous or papillose-scabridulous. |
||||||||||||||||||||||||||||
Leaves | ocrea 3–15 mm, proximal part cylindric or ± funnelform, distal part silvery, hyaline, soon disintegrating into persistent fibers or nearly completely deciduous; petiole 0.3–9 mm; blade green to gray-green, narrowly elliptic, lanceolate, elliptic, obovate, or spatulate, 6–50(–60) × 0.5–22 mm, margins flat, apex acute, obtuse, or rounded; stem leaves 1–4 times as long as adjacent branch leaves; distal leaves overtopping flowers. |
uniformly distributed, articulated to ocreae, basal leaves caducous or persistent, distal leaves abruptly reduced to bracts; ocrea 6–15 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part soon disintegrating into a few brown fibers; petiole 0.1–1 mm; blade 1-veined, with 1 pleat on each side of midrib, narrowly lanceolate to linear, 25–40 × 1–8 mm, margins usually flat, papillose-denticulate, apex mucronate or cuspidate. |
||||||||||||||||||||||||||||
Inflorescences | axillary; cymes uniformly distributed or aggregated at tips of stems and branches, 1–6(–8)-flowered. |
axillary and terminal, spikelike, slender, elongate; cymes spaced along branches, 1–2(–3)-flowered. |
||||||||||||||||||||||||||||
Pedicels | enclosed in or exserted from ocreae, 1.5–5 mm. |
enclosed in ocreae, erect, 1–1.5 mm. |
||||||||||||||||||||||||||||
Flowers | closed or semi-open; perianth 1.8–5.5 mm; tube 20–57% of perianth length; tepals overlapping or not, green or reddish brown with white, pink, or red margins, petaloid, not keeled, oblong to obovate, often cucullate in fruit; midveins branched or unbranched, thickened or not; stamens 5–8. |
closed; perianth 2.5–4.2 mm; tube 15–22% of perianth length; tepals overlapping, green, often brownish when dried, with pink or white margins, petaloid or sepaloid, elliptic, cucullate, navicular, apex rounded; midveins usually unbranched, rarely branched; stamens 8. |
||||||||||||||||||||||||||||
Achenes | enclosed in or exserted from perianth, light to dark brown, ovate, (2–)3-gonous, 1.2–4.2 mm, faces subequal or unequal, apex not beaked, edges slightly concave, dull, usually coarsely striate-tubercled, sometimes obscurely tubercled; late-season achenes common or not, 2–5 mm. |
enclosed in or slightly exserted from perianth, black, elliptic to oblong, 2.3–4 mm, faces subequal, shiny, smooth or minutely striate-tubercled near edges and apex. |
||||||||||||||||||||||||||||
2n | = 20. |
|||||||||||||||||||||||||||||
Polygonum aviculare |
Polygonum tenue |
|||||||||||||||||||||||||||||
Phenology | Flowering Jun–Oct. | |||||||||||||||||||||||||||||
Habitat | Dry acid soils in exposed sites | |||||||||||||||||||||||||||||
Elevation | 100-1000 m (300-3300 ft) | |||||||||||||||||||||||||||||
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; nearly worldwide
|
AL; AR; CT; DC; DE; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; NC; NE; NH; NJ; NY; OH; OK; PA; RI; SD; TN; TX; VA; VT; WI; WV; WY; ON
|
||||||||||||||||||||||||||||
Discussion | Subspecies 7+ (6 in the flora). Polygonum aviculare is a taxonomically controversial polyploid complex of selfing annuals. Although members of the complex have been considered inbreeders, they possess some structures that make cross pollination possible. Cleistogamous and chasmogamous flowers, heterostyly, protandry, and the capacity to secrete nectar suggest an ancestral mixed-mating system. Isoenzyme studies showed that the complex has an allopolyploid origin (P. Meerts et al. 1998) and has evolved as a swarm of inbreeding lines (“Jordanons”) (J. Gasquez et al. 1978). The six subspecies included here have been treated variously (T. Karlsson 2000; M. Costea and F. J. Tardif 2003). Complex intergradation patterns among them make their recognition at the species level impractical. Multivariate analysis and isoenzyme studies show that populations with intermediate characteristics may occur (Meerts et al. 1990, 1998). Except for subsp. boreale, which occurs in Greenland and Labrador, all subspecies are partially sympatric and their distributions have been influenced greatly by humans. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|||||||||||||||||||||||||||||
Key |
|
|||||||||||||||||||||||||||||
Source | FNA vol. 5, p. 556. | FNA vol. 5, p. 567. | ||||||||||||||||||||||||||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | ||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||||||||||
Synonyms | P. tenue var. protrusum | |||||||||||||||||||||||||||||
Name authority | Linnaeus: Sp. Pl. 1: 362. (1753) | Michaux: Fl. Bor.-Amer. 1: 238. (1803) | ||||||||||||||||||||||||||||
Web links |
|