Polygonum parryi |
Polygonum douglasii |
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Parry's knotweed, Parry's or prickly knotweed, prickly knotweed |
Douglas' knotweed, renouée de Douglas |
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Habit | Herbs, compact, often cushion-like. | Herbs. |
Stems | erect, green-brown, simple or branched from base, not wiry, 2–5(–8) cm, glabrous. |
erect, green, simple or branched, not wiry, 5–80 cm, glabrous or sparsely papillose-scabridulous. |
Leaves | ± uniformly distributed, dense, not articulated to ocreae, basal leaves ± persistent, distal leaves gradually reduced to bracts; ocrea 2–4(–5) mm, glabrous, proximal part cylindric, distal part deeply lacerate, disintegrating into white, curled fibers; petiole absent; blade 3-veined, without pleats, linear-lanceolate, subulate, 5–13(–20) × 0.4–1 mm, margins revolute, smooth, apex spine-tipped. |
uniformly distributed, articulated to ocreae, basal leaves caducous, distal leaves abruptly reduced to bracts; ocrea 6–12 mm, glabrous or minutely papillose-scabridulous, proximal part cylindric, distal part hyaline, lacerate; petiole 0.1–2 mm; blade 1-veined, not pleated, linear, narrow-oblong, or oblanceolate, 15–55 × 2–8(–12) mm, margins revolute, smooth or papillose-denticulate; apex acute to mucronate. |
Inflorescences | axillary; cymes in most axils, 1-flowered. |
axillary and terminal, spikelike, elongate; cymes widely spaced along branches, 2–4-flowered. |
Pedicels | absent. |
mostly exserted from ocreae, reflexed, 2–6 mm. |
Flowers | closed; perianth 1.5–2(–2.5) mm; tube 6–15% of perianth length; tepals overlapping, usually reddish with white margins, petaloid, oblong, navicular, apex acute; midveins unbranched; stamens 8. |
closed; perianth 3–4.5 mm; tube 20–28% of perianth length; tepals overlapping, green to tannish with white or pink margins, petaloid, oblong, cucullate, navicular, apex rounded; midveins usually branched, rarely unbranched; stamens 8. |
Achenes | slightly exserted from perianth at maturity, dark brown, ovate, 1.2–1.6(–2) mm, faces subequal, shiny, smooth. |
enclosed in perianth, black, elliptic or oblong to ovate, 3–4(–4.5) mm, faces subequal, shiny or dull, smooth or minutely striate-tubercled. |
Polygonum parryi |
Polygonum douglasii |
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Phenology | Flowering May–July. | Flowering Jun–Oct. |
Habitat | Vernally moist, open, sandy or rocky places | Dry, often disturbed places, rock outcrops, sandy ground |
Elevation | 500-2000 m (1600-6600 ft) | 300-3000 m (1000-9800 ft) |
Distribution |
CA; WA
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AZ; CA; CO; IA; ID; MI; MN; MT; NE; NH; NM; NV; NY; OR; SD; UT; VA; VT; WA; WY; AB; BC; MB; ON; QC; SK; YT
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Discussion | Five taxa that have been included in Polygonum douglasii (E. Murray 1982; J. C. Hickman 1984; J. T. Kartesz and K. N. Gandhi 1990) are treated here as distinct species: P. austiniae, P. majus, P. nuttallii, P. sawatchense, and P. spergulariiforme. Hickman noted extensive intergradation and numerous intermediate specimens among those sympatric elements, but qualitative or quantitative characters allow reliable discrimination in most cases (M. Costea and F. J. Tardif 2005), and species are here circumscribed similar to C. L. Hitchcock (1964). Greene described var. latifolium as having leaf blades and achenes broader than those of var. douglasii. C. L. Hitchcock (1964) recognized the former, but the characters used to distinguish it appear to vary continuously, and reliable separation is not possible. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 5, p. 563. | FNA vol. 5, p. 567. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia |
Sibling taxa | ||
Synonyms | P. douglasii var. latifolium, P. emaciatum, P. montanum, P. tenue var. commune, P. tenue var. latifolium | |
Name authority | Greene: Bull. Torrey Bot. Club 8: 99. (1881) | Greene: Bull. Calif. Acad. Sci. 1: 125. (1885) |
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