7b.1. Rosa (subg. Rosa) sect. Systylae de Candolle, Cat. Pl. Hort. Monsp. 137. 1813.
Shrubs, sometimes forming thickets; stoloniferous. Stems erect to procumbent, climbing, vinelike, (10–)15–30(–100) dm; distal branches glabrous, eglandular; prickles infrastipular and/or internodal, single or paired, usually curved or declined, sometimes erect, flattened, ± stout, sometimes mixed with aciculi, rarely absent. Leaves deciduous or semipersistent, 5–12 cm, membranous or leathery; stipules persistent, adnate to petiole, ˂auricles flared or erect˃, margins lacinulose, sometimes entire, eglandular or stipitate-glandular; leaflets 3–9(–11), terminal: petiolule 5–16 mm, blade elliptic, ovate, elliptic-ovate, or obovate, 10–48(–70) × 8–27(–40) mm, abaxial surfaces glabrous or pubescent to tomentose, eglandular, sometimes glandular, adaxial dull or lustrous. Inflorescences panicles, 1–6(–30+)-flowered. Pedicels erect, slender, 5–25 mm, glabrous or pubescent, eglandular or stipitate-glandular; bracts persistent, 1–3, margins lacinulose, stipitate-glandular. Flowers 1.5–5 cm diam.; hypanthium ovoid, oblong, or urceolate, glabrous, eglandular or stipitate-glandular; sepals persistent, reflexed, ovate-acuminate or -lanceolate, 6–18 × 1–4 mm, margins entire or (outer) pinnatifid, abaxial surfaces glabrous or pubescent, eglandular or stipitate-glandular; petals single or double, pink, rose-purple, or white; carpels 6–25, styles connate ˂in columns, exsert 3–6 mm, sometimes ± free with age˃, glabrous or pilose, stylar orifice 0.5–2 mm diam., hypanthial disc conic, 2–4 mm diam. Hips red or orange-red, usually globose, sometimes ovoid or subglobose, (4–)5–10 × 5–9 mm, glabrous, eglandular or sparsely stipitate-glandular; sepals late deciduous, reflexed. Achenes basiparietal.
Species ca. 35 (3 in the flora): North America, Europe, Asia (primarily China), n Africa; introduced in Mexico, West Indies, Central America, South America, Pacific Islands (New Zealand, Philippines).
Other species of sect. Systylae, hybrids, and cultivars that spread by stoloniferous shoots and are mostly sterile have escaped from cultivation and are occasionally found. One is Rosa sempervirens Linnaeus, evergreen rose, native to southern Europe, Asiatic Turkey, and northern Africa and found in California (B. Ertter and W. H. Lewis 2008); introduced in 1827 in France, it may also be the basis of a collection from Massachusetts (B. N. Gates 15713, 8 Nov. 1942, CONN), noted as doubtless an escape and spreading by rooting freely at tips of canes, and in Oklahoma, where a scrambling vine was collected (P. Kirtley 68, 6 Oct. 1935, MO). Such occasional findings of R. sempervirens can be expected in mostly warmer areas of the continent where it is readily recognized by its sprawling stems to 60 dm, and usually persistent, leathery, and lustrous leaflets with terminal leaflets distinctly longer than laterals. The species is introduced sporadically in the West Indies, Central America, and South America.
Rosa ×moschata Herrmann, musk rose, an escape from mostly southern latitude gardens, is found in Alabama, Illinois (not confirmed), and Louisiana. It is identified by long climbing or prostrate stoloniferous stems reaching 90 dm with erect or slightly curved prickles, leaflets ovate to lanceolate-elliptic, 5–50(–70) mm, mostly glabrous, finely serrate, and adaxially not lustrous, flowers to 5 cm diam. in clusters having a musky fragrance, petals white, or less commonly, pink, often double, sepals narrowly lanceolate and long-acuminate to 20 mm, strongly reflexed, dark red or purple-brown hips.