Persicaria hydropiper (L.) Spach

Almost glabrous annual herb; stems erect or suberect, to c. 75 cm tall, often reddish; roots rather slender. Lvs on main stem similar to those on branches, subsessile or shortly petiolate. Lamina 1–12 × 0.3–2 cm, lanceolate or linear-lanceolate, bright or deep green, with small translucent glandular dots; margins ciliolate and ± undulate; base cuneate to attenuate; apex obtuse to acuminate. Ochreae to 2 cm long, reddish brown, truncate, with 0-few fringing bristles, ± flared at upper nodes. Racemes slender, spike-like, to c. 7 cm long, at least partly curving downwards, the lower fls often distant; pedicels short, enclosed by bracts at anthesis, later protruding. Perianth 1.5–3 mm long, prominently dotted with brownish glands, usually pink or rose, rarely white, accrescent; segments ± broad-elliptic, strongly imbricate. Nut 2.5–3 mm long, trigonous or biconvex, dark brown or black, finely granular and appearing dull to moderately shining.

[From: Webb et al. (1985) Flora of New Zealand. Volume 4 as Polygonum hydropiper L.]