Vines. Stems annual, climbing, branching, to 2.5 m, herbaceous, glabrous; prickles absent. Leaves: petiole thin, 1-6 cm; tendrils numerous, long, functional; blade oblong-ovate, ovate, or round, 4.5-12 × 3-9 cm, glabrous abaxially, base cordate to truncate, margins entire, apex obtuse to acute; proximal cauline leaves narrower and smaller. Umbels many, axillary to leaves, 20-100+-flowered, globose; peduncle to 30 cm, progressively shorter distally. Flowers: perianth greenish, carrion-scented; tepals 3.5-4.5 mm; anthers much shorter than filaments; ovules (1-)2 per locule; pedicel 0.5-2 cm. Berries blue, subglobose, ca. 10 mm diam., glaucous. 2n = 26. Flowering May--Jun. Higher elevations in rich woods, alluvial thickets, and meadows, often in calcareous soils; 100--800 m; N.B., Ont., Que; Ala., Ga., Ky., Maine, Md., Mass., N.H., N.Y., N.C., Ohio, Pa., S.C., Tenn., Vt., Va., W.Va. The leaves and habit of Smilax herbacea are quite variable.
From Flora of Indiana (1940) by Charles C. Deam
This plant is variable in size and in its habitat. I found a specimen in Franklin County that was 15 feet long. On the whole, plants of the variety are larger than those of the typical form. It is infrequent to rare throughout the state and is found on wooded slopes and alluvial plains, and rarely in the open, usually associated with beech and white oak.
Herbaceous, unarmed, climbing to 2.5 m, often freely branched; lvs numerous (more than 25), most of them with tendrils, at base cordate to rounded, at apex acuminate to cuspidate or broadly rounded, always with convex lateral margins; peduncles numerous, individually axillary to the foliage-lvs, flattened, with numerous (mostly more than 25) fls; tep 3.5-5 mm; anthers 1-2 mm; fr 8-10 mm; seeds 3-6; 2n=26. Moist soil of open woods, roadsides, and thickets. May, June. Three vars..
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.