Vines; rhizomes linear. Stems perennial, climbing, branching, terete to quadrangular, 5-6+ m × 6 mm, woody, glabrous; prickles green with dark tips, stout, to 12 mm. Leaves deciduous to evergreen, ± evenly disposed; petiole 0.5-1.5 cm; tendrils numerous; blade variable, bright green, drying to pale to brownish green, usually ovate to broadly ovate, with 3 (or 5) ± prominent veins, 4-17 × 4-16 cm, lustrous, not glaucous, glabrous abaxially, base cordate to rounded with acute insertion at petiole, margins entire, apex abruptly pointed. Umbels numerous, axillary to leaves, 5-12(-20)-flowered, open to dense, hemispherical to spherical; peduncle to 1.5 cm, longer or shorter than petiole of subtending leaf. Flowers: perianth pale yellowish green to bronze; tepals 3-4 mm; anthers shorter than to ± equaling filaments; ovule 1 per locule; pedicel 0.2-1.5 cm. Berries blue-black to black, globose, 5-8 mm, glaucous. 2n = 32. Flowering Apr--Jun. Dry to moist, sometimes riparian woods, borders, hedgerows, thickets; 0--200 m; N.S., Ont.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va. Normally, the peduncle of Smilax rotundifolia is about the same length as the petiole of the subtending leaf. In exceptional cases, the peduncle may be considerably longer, thereby making this widely distributed species difficult to distinguish from S. bona-nox and S. tamnoides. It lacks the marginal cartilaginous band found on the leaves of the former species and the hispid prickles of the stem of the latter. Specimens of S. tamnoides lacking prickles may be distinguished by their more strongly ridged stems.
Perennial woody vine to over 6 m tall Stem: climbing, branching, hairless, with stout flattened prickles that are green with dark tips. Leaves: alternate, stalked, shiny bright green, 4 - 17 cm long, 4 - 16 cm wide, egg-shaped to kidney-shaped or nearly round with a heart-shaped to rounded or squared base and a pointed to rounded tip often with an abrupt point (cusp), having three to seven prominent veins with smaller interconnecting veins beneath. Flowers: either male or female, found on separate plants (dioecious), borne on an inflorescence with branches radiating from a common point (umbel). The numerous open to dense umbels are borne axillary to the leaves, each being hemispherical to spherical and having five to twenty flowers with six pale yellowish green to bronze tepals 3 - 4 mm long. Fruit: a bluish black to black berry, 5 - 8 mm long, spherical, covered with a whitish waxy coating (glaucous), containing two to three seeds. Tendrils: numerous.
Similar species: Smilax rotundifolia and Smilax hispida are vines with woody stems. Smilax hispida is distinguished from S. rotundifolia by its flexible needle-like prickles and its one- to two-seeded fruit that lacks a whitish waxy coating (glaucous).
Flowering: late May to early June
Habitat and ecology: Frequent in mesic woods of the eastern Chicago Region, this species also grows on shaded dune slopes, hummocks of swampy dune woodlands, and dune savannas.
Occurence in the Chicago region: native
Etymology: Smilax is the ancient Greek name of an evergreen oak. Rotundifolia means round-leaved.
Slender woody vine; stems usually quadrangular, diffusely branched and often climbing high, with scattered stout, flattened prickles below; lvs deciduous, thin, green, shining, ovate to rotund or triangular-ovate, 5-10 נ4-9 cm, or smaller in dry soils, acute to cuspidate or obtuse, entire or rarely sparsely roughened on the margins, at base broadly rounded to truncate or cordate, 5- or 7-nerved, reticulate beneath at maturity; peduncles flattened, about as long as the subtending petioles; staminate tep recurved only above the middle; fr black, usually glaucous, mostly 2-3-seeded; 2n=32. Open woods, thickets, and roadsides; N.S. to n. Fla., w. to Mich., se. Mo., e. Okla., and e. Tex., the commonest greenbrier in the ne. part of our range. May, June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.