Polygonum californicum |
Polygonum oxyspermum |
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California knotweed |
knotweed, sharp-fruit knotweed |
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Habit | Herbs. | Plants green to blue-green, homophyllous. | ||||
Stems | erect, green, simple or divaricately branched, ± wiry, 4–40 cm, papillose-scabridulous. |
prostrate to ascending, branched at proximal and middle nodes, not wiry, 20–100 cm. |
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Leaves | uniformly distributed, not articulated to ocreae, basal leaves usually caducous, distal leaves abruptly reduced to bracts; ocrea 5–10 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part white or tawny, disintegrating into ± bristly-fringed fibers; petiole absent; blade 3-veined, without pleats, linear, 5–25(–30) × 0.5–2 mm, margins revolute, papillose-denticulate or smooth, apex mucronate or weakly spine-tipped. |
ocrea 6.5–12 mm, proximal part cylindric, pruinose, distal part hyaline, soon disintegrating into brown fibers or nearly completely deciduous; petiole 0–1 mm; blade green to bluish green, elliptic-lanceolate to linear, 10–35 × 1.5–15 mm, margins flat or narrowly revolute, apex acute; middle stem leaves slightly larger than adjacent branch leaves, distal leaves overtopping flowers. |
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Inflorescences | axillary; cymes in distal axils, 1-flowered. |
axillary, cymes uniformly distributed, 2–7-flowered. |
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Pedicels | absent. |
exserted from ocreae, 2.5–5(–7) mm. |
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Flowers | open or closed; perianth 2.5–3.5 mm; tube 10–20% of perianth length; tepals overlapping, uniformly white to pink, petaloid, elliptic, navicular, apex acute to acuminate; midveins unbranched; stamens 8. |
semi-open; perianth 3.5–5.5 mm; tube 28–39% of perianth length; tepals slightly overlapping, green, margins white to pink, petaloid, not keeled, oblong to obovate, not cucullate; veins branched; stamens 8. |
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Achenes | enclosed in or slightly exserted from perianth, brown, narrowly elliptic, 1.8–2.2 mm, faces subequal, shiny, smooth. |
exserted from perianth, pale brown to dark brown, ovate, 3-gonous, (3.5–)4.1–5.5(–6.5) mm, faces subequal, apex not beaked, edges straight, shiny, smooth or with fine tubercles especially toward apex; late-season achenes unknown. |
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Polygonum californicum |
Polygonum oxyspermum |
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Phenology | Flowering May–Sep. | |||||
Habitat | Open places, including serpentine | |||||
Elevation | 40-1200 m (100-3900 ft) | |||||
Distribution |
CA; OR
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ME; NB; NF; NS; PE; QC; Europe |
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Discussion | Subspecies 3 (2 in the flora). The treatment by D. A. Webb and A. O. Chater (1963) of the Polygonum oxyspermum complex is followed here. T. Karlsson (2000) accepted P. raii and P. oxyspermum as distinct species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 564. | FNA vol. 5, p. 554. | ||||
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Duravia californica, P. greenei | |||||
Name authority | Meisner: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 100. (1856) | C. A. Meyer & Bunge ex Ledebour: Index Seminum (Dorpat) 1824: 5. (1824) | ||||
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