Polygonum aviculare subsp. boreale

(Lange) Karlsson

Svensk Bot. Tidskr. 91: 249. 1998.

Common names: Northern knotweed
Basionym: Polygonum aviculare var. boreale Lange Consp. Fl. Groenland. 1: 105. 1880
Synonyms: Polygonum arenastrum subsp. boreale (Lange) Á. Löve Polygonum boreale Lindman Polygonum heterophyllum subsp. boreale (Lange) Á. Löve & D. Löve
Treatment appears in FNA Volume 5. Treatment on page 557. Mentioned on page 556.

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


V5 1138-distribution-map.gif

Greenland, Nfld. and Labr. (Labr.), nw Europe.


Selected References


Lower Taxa

Mihai Costea +, François J. Tardif +  and Harold R. Hinds† +
(Lange) Karlsson +
Polygonum aviculare var. boreale +
Northern knotweed +
Greenland +, Nfld. and Labr. (Labr.) +  and nw Europe. +
0-500 m +
Sandy, gravelly, or rocky coastal areas +
Flowering Aug–Oct. +
Svensk Bot. Tidskr. +
Polygonum arenastrum subsp. boreale +, Polygonum boreale +  and Polygonum heterophyllum subsp. boreale +
Polygonum aviculare subsp. boreale +
Polygonum aviculare +
subspecies +