Galium aparine L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - 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. Plants with 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)