Polygonum majus |
Polygonum nuttallii |
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large Douglas' knotweed, large knotweed, Palouse knotweed, wiry knotweed |
Nuttall's knotweed |
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Habit | Herbs. | Herbs. |
Stems | erect, green, simple or branched, ± wiry, 15–60 cm, usually papillose-scabridulous. |
spreading to erect, sometimes zigzagged, purplish, simple or branched, wiry, (5–)10–35 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. |
evenly distributed or crowded at branch tips, articulated to ocreae, basal leaves persistent, distal leaves gradually reduced to bracts; ocrea 3–4 mm, papillose-scabridulous, proximal part funnelform, distal part finely lacerate; petiole 0.1–2 mm; blade 1-veined, not pleated, linear to narrowly oblong-elliptic, 8–30 × 1–4(–7) mm, margins narrowly revolute, never touching along midrib, smooth, apex acute, mucronate, ± glaucous adaxially. |
Inflorescences | axillary and terminal, spikelike, elongate; cymes spaced along branches, 2–5-flowered. |
axillary and terminal, spikelike, dense; cymes mostly congested toward tips of branches, 2–3-flowered. |
Pedicels | exserted from ocreae, reflexed, 0.5–1 mm. |
enclosed in ocreae, erect to spreading, 2–3 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 or closed; perianth 1.8–2.4 mm; tube 25–33% of perianth length; tepals overlapping, greenish, white, or pink with pink margins, petaloid, oblong, cucullate, navicular in distal 1/4, apex rounded; midveins unbranched; stamens 8. |
Achenes | enclosed in perianth, black, elliptic, 3.5–5 mm, faces subequal, shiny or dull, smooth or striate-tubercled. |
enclosed in perianth, black, elliptic to ovate, 1.8–2.3 mm, faces subequal, shiny, smooth. |
Polygonum majus |
Polygonum nuttallii |
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Phenology | Flowering May–Aug. | Flowering May–Oct. |
Habitat | Dry plains, meadows, sometimes on serpentine | Dry prairies, open knolls in lower mountains, open sites in lowland and montane zones, sandy soil |
Elevation | 500-2000 m (1600-6600 ft) | 800-1100 m (2600-3600 ft) |
Distribution |
CA; CO; ID; NV; OR; UT; WA; WY; BC
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OR; WA; BC
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Discussion | C. L. Hitchcock (1964) suggested that Polygonum nuttallii is but a small-flowered form of P. spergulariiforme. Although morphologically similar, P. nuttallii differs from P. spergulariiforme in some respects, including its wiry, purplish stems, short and funnelform ocreae, adaxially glaucous leaves, longer bracts, shorter fruiting perianth, and achenes. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 5, p. 570. | FNA vol. 5, p. 570. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia |
Sibling taxa | ||
Synonyms | P. coarctatum var. majus, P. douglasii subsp. majus | P. intermedium, P. douglasii subsp. nuttallii |
Name authority | (Meisner) Piper: Fl. Palouse Reg., 63. (1901) | Small: Mongr. Amer. Sp. Polygonum, 132, plate 53. (1895) |
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