Persicaria attenuata subsp. attenuata

Erect to decumbent perennial herb to c. 1 m high; stems becoming inflated and floating, up to 3 m long when plants are submerged, glabrous or with scattered hairs. Ochreas glabrous or with appressed hairs on sheath, apex sometimes ciliate. Leaves narrowly ovate, ± falcate, 5–20 cm long, 15–50 mm wide; variably pubescent, usually at least the margins and main veins with long white appressed hairs, lamina glabrous to subvillous, usually densely gland-dotted on the lower surface, less often glandular above; petiole 10–40 mm long. Inflorescence of 2–4 well spaced, dense cylindrical spikes, 4–13 cm long, 6–10 mm diam., peduncle 4–5 cm long; perianth segments 3–5 mm long, white, or somewhat greenish, free for half to two-thirds their length. Nut lenticular, 2.0–2.5 mm long and wide, dark brown to blackish. Flowers Apr.–Sep. (2 records).