Polygonum majus |
Polygonum plebeium |
|
---|---|---|
large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
common knotweed |
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Habit | Herbs. | Plants bluish green, homophyllous. |
Stems | erect, green, simple or branched, ± wiry, 15–60 cm, usually papillose-scabridulous. |
prostrate, much-branched from base, not wiry, 10–40 cm, papillose-scabridulous. |
Leaves | uniformly distributed, articulated to ocreae, basal leaves often caducous, distal leaves abruptly reduced to bracts, articulated to ocreae; ocrea 5–12 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part lacerate or disintegrating into fibers; petiole 0.1–2 mm; blade 1-veined, not pleated, linear to narrowly oblong or lanceolate, 15–70 × 2–8 mm, margins revolute, papillose-denticulate, apex acute or mucronate. |
ocrea 1-veined, 2.5–3 mm, proximal part cylindric, distal part laciniate; petiole 0–1 mm; blade bluish green, narrowly elliptic or oblanceolate, 5–16 × 1–4 mm, margins flat, apex obtuse or acute, papillose-scabridulous; stem leaves 1–1.5(–2) times longer than adjacent branch leaves, distal leaves overtopping flowers. |
Inflorescences | axillary and terminal, spikelike, elongate; cymes spaced along branches, 2–5-flowered. |
axillary; cymes uniformly distributed, 3–6-flowered. |
Pedicels | exserted from ocreae, reflexed, 0.5–1 mm. |
exserted from ocreae, 3–5 mm. |
Flowers | open or semi-open; perianth (3.5–)4–5 mm; tube 9–17% of perianth length; tepals overlapping, uniformly white to pink, petaloid, oblong to oblong-obovate, cucullate, navicular in distal 1/4, apex rounded; midveins unbranched or with short lateral branches; stamens 8. |
closed; perianth 1–1.5 mm; tube 12–27% of perianth length; tepals overlapping, green with white or pink margins, petaloid, not keeled, elliptic, cucullate; midveins unbranched, thickened; stamens 5. |
Achenes | enclosed in perianth, black, elliptic, 3.5–5 mm, faces subequal, shiny or dull, smooth or striate-tubercled. |
enclosed in perianth, black-brown, broadly ovate, 2–3-gonous, 1.5–2 mm, faces subequal, apex not beaked, edges concave, shiny, smooth; late-season achenes common, 2–4 mm. |
2n | = 20. |
|
Polygonum majus |
Polygonum plebeium |
|
Phenology | Flowering May–Aug. | Flowering May–Oct. |
Habitat | Dry plains, meadows, sometimes on serpentine | Disturbed sites |
Elevation | 500-2000 m (1600-6600 ft) | 50-500 m (200-1600 ft) |
Distribution |
CA; CO; ID; NV; OR; UT; WA; WY; BC
|
ID; e Africa; s Asia; Australia [Introduced in North America] |
Source | FNA vol. 5, p. 570. | FNA vol. 5, p. 556. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum |
Sibling taxa | ||
Synonyms | P. coarctatum var. majus, P. douglasii subsp. majus | |
Name authority | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) | R. Brown: Prodr., 420. (1810) |
Web links |
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