Polygonum bidwelliae |
Polygonum glaucum |
|
---|---|---|
Bidwell knotweed, Bidwell's knotweed |
seabeach knotweed, seaside knotweed |
|
Habit | Herbs. | Plants silvery, homophyllous. |
Stems | erect, green, simple or divaricately branched, ± wiry, 2–20 cm, minutely papillose-scabridulous. |
prostrate to ascending, branched from base, not wiry, 20–70 cm. |
Leaves | crowded at branch tips, not articulated to ocreae, basal leaves caducous or persistent, distal leaves abruptly reduced to bracts; ocrea 8–13 mm, papillose-scabridulous, proximal part cylindric, distal part overlapping and obscuring leaves and flowers, silvery, entire or shallowly dentate; petiole absent; blade 3-veined, without pleats, linear, 5–15(–20) × 0.5–1.5(–2) mm, margins revolute, papillose-denticulate, apex spine-tipped. |
ocrea persistent, 7–15 mm, proximal part cylindric, pruinose, distal parts silvery, margins overlapping, entire or lacerate; petiole 0.5–3 mm; blade bluish green, lanceolate, 10–30 × 2–8 mm, coriaceous, margins revolute, apex obtuse or acute, rugulose when fresh, markedly rugulose when dried, glaucous; middle stem leaves slightly larger than adjacent branch leaves, distal leaves overtopping flowers they subtend. |
Inflorescences | axillary; cymes in distal axils, 1-flowered. |
axillary; cymes uniformly distributed, 1–3-flowered. |
Pedicels | absent. |
enclosed in ocreae, 3–5 mm. |
Flowers | closed; perianth 2–3 mm; tube 10–18% of perianth length; tepals overlapping, pink with pink or white margins, petaloid, elliptic, navicular, apex acute to acuminate; midveins unbranched; stamens 8. |
semi-open; perianth (2–)3–4 mm; tube 12–26% of perianth length; tepals ± recurved, overlapping, white, margins white or pink, petaloid, not keeled, oblong-obovate to spatulate, not cucullate; midvein usually unbranched; stamens 8. |
Achenes | enclosed in perianth at maturity, light brown to brown, ovate-elliptic, 1.8–2.3 mm, faces subequal, shiny, smooth. |
exserted from perianth, reddish brown to dark brown, ovate, 3-gonous, 2.5–3(–4) mm, faces subequal, apex not beaked, edges straight, shiny, smooth; late-season achenes common, 3–5 mm. |
2n | = 40. |
|
Polygonum bidwelliae |
Polygonum glaucum |
|
Phenology | Flowering May–Jun. | Flowering Jul–Nov. |
Habitat | Thin volcanic soils, chaparral, montane woodland valleys, grasslands | Coastal beaches, sand dunes, margins of salt ponds |
Elevation | 60-1200 m (200-3900 ft) | 0-10 m (0-0 ft) |
Distribution |
CA
|
CT; DC; DE; FL; GA; MA; MD; NC; NJ; NY; RI; SC; VA |
Discussion | Polygonum bidwelliae occurs in the Cascade Range and northeastern Sacramento Valley in Butte, Shasta, and Tehama counties. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Polygonum glaucum is restricted to maritime beaches along the Atlantic coast from Massachusetts south to Georgia. Over most of its range it is rare and declining; populations on coastal islands of Massachusetts and along the shore of Long Island appear to be secure. Seabeach knotweed appears to be related to P. oxyspermum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 5, p. 565. | FNA vol. 5, p. 553. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Duravia | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum |
Sibling taxa | ||
Name authority | S. Watson: Proc. Amer. Acad. Arts 14: 294. (1879) | Nuttall: Gen. N. Amer. Pl. 1: 254. (1818) |
Web links |