Ray's knotweed, renouée de Ray

Polygonum raii Babington, Trans. Linn. Soc. London 17: 458. 1836

Leaves: ocrea not prominently veined, 7-10 mm, distal part disintegrating, nearly completely deciduous; blade bluish green, elliptic, 3.5-5 times as long as wide. Flowers: perianth (3.5-)4-5 mm; tepals overlapping, green with white or pink margins, obovate, apex flat, flared. Achenes with apex exserted 0.5-1.3(-1.8) mm from perianth, (3.5-)4-5 mm, 1.3-1.6 times as long as wide, ± smooth or finely striate-tubercled. 2n = 40.

Flowering Jul-Oct. Coastal beaches, dunes, and shores; 0-10 m; introduced; St. Pierre and Miquelon; N.B., Nfld. and Labr. (Nfld.), N.S., P.E.I., Que., Maine; Europe.

Some sources consider subsp. raii to be native in North America.