Polygonum argyrocoleon |
Polygonum glaucum |
|
---|---|---|
Persian knotweed, silver sheath knotweed |
seabeach knotweed, seaside knotweed |
|
Habit | Plants green, heterophyllous. | Plants silvery, homophyllous. |
Stems | erect or decumbent, branched mostly from base, not wiry, 15–100 cm. |
prostrate to ascending, branched from base, not wiry, 20–70 cm. |
Leaves | ocrea 4–8 mm, proximal part cylindric, distal part soon disintegrating into curly or straight fibers; petiole 0–1.5 mm; blade bluish green, lanceolate or linear-lanceolate, 15–50 × 2–8 mm, margins flat, apex acute; stem leaves 2.1–4 times as long as branch leaves; distal leaves abruptly reduced and not overtopping flowers (shorter than or equaling flowers). |
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. |
Inflorescence(s) | axillary and terminal, spikelike; cymes aggregated at tips of stems and branches, 4–6-flowered, bracts inconspicuous. |
axillary; cymes uniformly distributed, 1–3-flowered. |
Pedicels | enclosed in ocreae, 1–2 mm. |
enclosed in ocreae, 3–5 mm. |
Flowers | closed; perianth 1.8–2.4 mm; tube 10–22% of perianth length; tepals overlapping, green or white, usually with pink, rarely red or white, margins, petaloid, not keeled, oblong to obovate, cucullate; midveins usually unbranched; stamens 7–8. |
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, brown, ovate, 3-gonous, 1.3–2.3 mm, faces subequal, slightly concave, apex not beaked, with concave edges, shiny, smooth; late-season achenes unknown. |
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 argyrocoleon |
Polygonum glaucum |
|
Phenology | Flowering May–Oct. | Flowering Jul–Nov. |
Habitat | Fields, gardens, disturbed sites, often in saline soils | Coastal beaches, sand dunes, margins of salt ponds |
Elevation | 0-1200 m (0-3900 ft) | 0-10 m (0-0 ft) |
Distribution |
AZ; CA; CO; FL; ID; LA; MA; MO; NC; NM; NV; TX; UT; VT; WV; c Asia [Introduced in North America]
|
CT; DC; DE; FL; GA; MA; MD; NC; NJ; NY; RI; SC; VA |
Discussion | 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. 560. | FNA vol. 5, p. 553. |
Parent taxa | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum | Polygonaceae > subfam. Polygonoideae > Polygonum > sect. Polygonum |
Sibling taxa | ||
Name authority | Steudel ex Kunze: Linnaea 20: 17. (1847) | Nuttall: Gen. N. Amer. Pl. 1: 254. (1818) |
Web links |