Polygonum marinense

T. R. Mertens & P. H. Raven

Madroño 18: 87. 1965.

Common names: Marin knotweed
IllustratedEndemicConservation concern
Treatment appears in FNA Volume 5. Treatment on page 552. Mentioned on page 548, 550, 553.

Plants often reddish tinged, heterophyllous, subsucculent. Stems prostrate to ascending, branching from base, not wiry, 15–40 cm. Leaves: ocrea 4–6 mm, proximal part funnelform, distal part silvery hyaline, soon disintegrating, leaving almost no fibrous remains; petiole 2–5 mm; blade often reddish tinged, elliptic to obovate or oblanceolate; 20–35 × 9–16 mm, margins flat, apex rounded; stem leaves (1.3–)2–2.6(–3.5) times as long as branch leaves; distal leaves overtopping flowers in distal part of inflorescence. Inflorescences axillary; cymes in most leaf axils, 1–4-flowered. Pedicels mostly exserted from ocreae, 2–4 mm. Flowers semi-open; perianth 3–3.5(–4) mm; tube 18–25% of perianth length; tepals overlapping, green, margins white or pink, petaloid, not keeled, broadly rounded, cucullate; midveins unbranched; stamens 8. Achenes exserted from perianth, brown, ovate, 3-gonous, 2.8–3.4(–4) mm, faces subequal or evidently unequal, apex not beaked, edges straight, shiny, minutely roughened; late-season achenes uncommon, 4.5–5 mm. 2n = 60.

Phenology: Flowering Apr–Oct.
Habitat: Coastal salt and brackish marshes, swamps
Elevation: 0-10 m


Of conservation concern.

The origin and taxonomic affinities of Polygonum marinense are uncertain. T. R. Mertens and P. H. Raven (1965) suggested a relationship with P. oxyspermum C. A. Meyer & Bunge or the Mediterranean P. robertii Loiseleur-Deslongchamps. Polygonum marinense may be confused with P. ramosissimum. It can be distinguished by its subsucculent texture, funnelform ocreae, leaves rounded at the apices, and semi-open flowers. Marin knotweed is known from fewer than 15 locations in Marin, Napa, Solano, and Sonoma counties; it is threatened by coastal development.

Selected References


Lower Taxa

... more about "Polygonum marinense"
Mihai Costea +, François J. Tardif +  and Harold R. Hinds† +
T. R. Mertens & P. H. Raven +
Marin knotweed +
0-10 m +
Coastal salt and brackish marshes, swamps +
Flowering Apr–Oct. +
Illustrated +, Endemic +  and Conservation concern +
Polygonum marinense +
Polygonum sect. Polygonum +
species +