Polygonum tenue Michx.

Herbs. Stems erect, green or brown-ish, simple or branched from below middle, not wiry, 5-50 cm, glabrous or papillose-scabridulous. Leaves uniformly distributed, articulated to ocreae, basal leaves caducous or persis-tent, distal leaves abruptly reduced to bracts; ocrea 6-15 mm, glabrous or papillose-scabridulous, proximal part cylindric, distal part soon disintegrating into a few brown fibers; petiole 0.1-1 mm; blade 1-veined, with 1 pleat on each side of midrib, narrowly lanceolate to linear, 25-40 × 1-8 mm, margins usually flat, papillose-denticulate, apex mucronate or cuspidate. Inflorescences axillary and terminal, spikelike, slender, elongate; cymes spaced along branches, 1-2(-3)-flowered. Pedicels enclosed in ocreae, erect, 1-1.5 mm. Flowers closed; perianth 2.5-4.2 mm; tube 15-22% of perianth length; tepals overlapping, green, often brownish when dried, with pink or white margins, petaloid or sepaloid, elliptic, cucullate, navicular, apex rounded; midveins usually unbranched, rarely branched; stamens 8. Achenes enclosed in or slightly exserted from perianth, black, elliptic to oblong, 2.3-4 mm, faces subequal, shiny, smooth or minutely striate-tubercled near edges and apex. 2n = 20.

Ont.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis., Wyo.

Flowering Jun-Oct.

Dry acid soils in exposed sites; 100-1000m.

Polygonum tenue var. protrusum Fernald

Polygonum tenue, the slender knotweed or pleat-leaf knotweed, is a North American species of plants in the buckwheat family. it is widespread across south-central Canada (Ontario) and the eastern and central United States from Maine to Georgia, west as far as Minnesota, South Dakota, Nebraska, and Texas (though apparently now extirpated from Maine and New Hampshire).

Polygonum tenue is a herb up to 50 cm (20 in) tall. Stems are green or brown, not wiry. Leaves are narrow, up to 4 cm (1.6 in) long. Flowers are pink or white.

Polygonum tenue là một loài thực vật có hoa trong họ Rau răm. Loài này được Michx. miêu tả khoa học đầu tiên năm 1803.