Polygonum aviculare subsp. boreale
Svensk Bot. Tidskr. 91: 249. 1998.
Plants green, homophyllous or subheterophyllous. Stems 1–7, prostrate to ascending, mostly branching from base, 6–50(–90) cm. Leaves: ocrea 3.5–7 mm, proximal part cylindric to funnelform, distal part soon disintegrating, nearly completely deciduous; petiole 7–9 mm; blade green, lateral veins visible but not raised abaxially, obovate-spatulate or oblanceolate, (12.5–)16–44(–55) × (4–)6–18(–22) mm, 2–4(–5.5) times as long as wide, apex obtuse to rounded; stem leaves (1.1–)1.3–2.5(–3) times as long as branch leaves. Cymes uniformly distributed, rarely crowded at tips of stems and branches, (3–)4–7-flowered. Pedicels mostly exserted from ocreae, 2–5 mm. Flowers: perianth 3.3–5.5 mm, 1.6–2.8 times as long as wide; tube 25–35(–39)% of perianth length; tepals overlapping, green with white or pink margins, obovate, flat or curved outward in fruit, outer tepals not pouched at base; veins branched, thickened; stamens 6–8. Achenes enclosed in perianth, dark brown, ovate, 3-gonous, (2.5–)2.7–4(–4.2) mm, faces subequal, concave, apex straight, coarsely striate-tubercled; late-season achenes uncommon, 4–5 mm. 2n = 40.
Phenology: Flowering Aug–Oct.
Habitat: Sandy, gravelly, or rocky coastal areas
Elevation: 0-500 m
Greenland, Nfld. and Labr. (Labr.), nw Europe.