Polygonum majus |
Polygonum striatulum |
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large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
striped knotweed, Texas knotweed |
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Habit | Herbs. | Plants perennial, light green, heterophyllous; rhizomes brown, 0.7–3 cm diam. |
Stems | erect, green, simple or branched, ± wiry, 15–60 cm, usually papillose-scabridulous. |
erect to ascending, sparingly branched in distal 1/2, not wiry, 25–60 cm. |
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 6–12 mm, proximal part cylindric, distal part soon disintegrating into brown fibers, later leaving almost no fibrous remains; petiole 0–2 mm; blade light green, linear-lanceolate to oblanceolate, 8–35 × 2–8 mm, margins flat, apex acute or obtuse; stem leaves 2.1–4 times as long as adjacent branch leaves; distal leaves sharply reduced, not overtopping flowers (shorter than or equaling flowers). |
Inflorescences | axillary and terminal, spikelike, elongate; cymes spaced along branches, 2–5-flowered. |
axillary and terminal, spikelike; cymes in distal nodes, 2–6-flowered. |
Pedicels | exserted from ocreae, reflexed, 0.5–1 mm. |
exserted from ocreae, 2–4 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. |
semi-open; perianth 2–3.5 mm; tube 18–25% of perianth length; tepals overlapping, green with white or sometimes pink margins, petaloid, not keeled, oblong to obovate, cucullate; midveins usually unbranched; stamens 7–8. |
Achenes | enclosed in perianth, black, elliptic, 3.5–5 mm, faces subequal, shiny or dull, smooth or striate-tubercled. |
enclosed in perianth, brown, ovate, 3-gonous, (1.6–)1.8–2.6(–3) mm, faces subequal or unequal, apex not beaked, edges concave, shiny, smooth or roughened; late-season achenes common, 4–6 mm. |
Polygonum majus |
Polygonum striatulum |
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Phenology | Flowering May–Aug. | Flowering Dec–Mar or Jun–Oct. |
Habitat | Dry plains, meadows, sometimes on serpentine | Seasonal moist places, sterile prairies, granitic soils |
Elevation | 500-2000 m (1600-6600 ft) | 100-700 m (300-2300 ft) |
Distribution |
CA; CO; ID; NV; OR; UT; WA; WY; BC
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TX |
Discussion | Plants with leaves less-conspicuously veined, flowering August to October, and growing in seasonally moist habitats in central and western Texas are recognized by some authors as Polygonum texense or P. striatulum var. texense (M. Costea and F. J. Tardif 2003). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 5, p. 570. | FNA vol. 5, p. 550. |
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 | P. striatulum var. texense, P. texense |
Name authority | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) | B. L. Robinson: Proc. Boston Soc. Nat. Hist. 31: 263. (1904) |
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