Herbs, annual, procumbent or clambering. Stems 30-90 cm high, 4-angled, 1-4 mm in diam., branched from base, retrorsely aculeate along angles, glabrescent to pilose at nodes. Leaves at middle stem region in whorls of 6-10, subsessile; blade drying papery, narrowly oblanceolate to narrowly oblong-oblanceolate, 10-60 × 3-10 mm, usually somewhat pilosulous or hispidulous adaxially, retrorsely aculeolate along midrib abaxially, base acute, margins flat to thinly revolute, retrorsely aculeolate, apex acute and shortly mucronate; vein 1. Inflorescences terminal and axillary, cymes 2- to several flowered; axes glabrous to aculeolate; bracts ± leaflike or none, 1-5 mm; peduncles 1-5 cm; pedicels 1-30 mm, finally elongating and sometimes curved directly under fruit. Ovary subglobose, 0.3-0.5 mm, with uncinate trichomes. Flowers hermaphroditic. Corolla yellowish green or white, rotate, 1.5-2 mm in diam.; lobes 4, triangular to ovate, acute. Mericarps subglobose to kidney-shaped, 2.5-5 mm, with a dense cover of uncinate trichomes 0.4-1.2 mm from swollen base. Fl. Mar-Jul, fr. Apr-Nov.
"Annual 1–10 dm, the stems weak, retrorsely hooked-scabrous on the angles, ± scrambling, seldom much branched; lvs in whorls of (6)8, narrow, 1-nerved, cuspidate, 1–8 cm, retrorsely scabro-ciliate on the margins and often also on the midvein beneath, uncinate-hispid above; infls mostly 3–5-fld, on axillary peduncles or in 3’s on short branches; cor white, 4-parted, 1–2 mm wide; fr uncinate-hispid, or rarely smooth. Damp ground, usually in shade; circumpolar, and found over most of temperate N. Amer. Plants with relatively large frs (mostly 2.8–4 mm, exclusive of the bristles), and with lvs to 8 cm, said to be mainly tetraploid to octoploid (on x=11) are var. aparine. Plantswith smaller frs (mostly 2–3 mm), and the lvs not over 4 cm, said to have usually 2n=20, but sometimes to 2n=66, are var. echinospermum (Wallr.) Farw. (G. spurium; G. vaillantii)"