Rosa sect. Rosa

Shrubs or subshrubs, forming dense, clumped thickets, colonies, or hedge clusters, miniatures forming small, low-clustered, or open habits; usually rhizomatous. Stems erect, flexuous, spreading, ascending, sprawling, or procumbent, 1–50 dm; distal and fertile branches glabrous, rarely puberulent to tomentose, eglandular; prickles infrastipular, single or paired (rarely to 3 in R. californica, to 4 in R. gymnocarpa), erect, curved, hooked, declined, introrse, appressed, thin, terete, deltate, subulate, stout, sparse, internodal similar, smaller, sometimes mixed with aciculi, rarely absent. Leaves deciduous, (2–)4–11(–17) cm, leathery to membranous; stipules persistent, adnate to petiole, auricles usually flared or erect, margins entire or serrate, sometimes serrulate, undulate, or sinuate, usually glandular; leaflets (3–)5–9(–11), terminal: petiolule 1–15(–20) mm, blade elliptic, lanceolate, obovate, or ovate, sometimes cordate, ovoid, oblong, or orbiculate, (4–)10–40(–63) × (3–)5–40 mm, rugose in R. rugosa, abaxial surfaces sometimes glaucous, glabrous or pubescent, eglandular, sessile-, or stipitate-glandular, adaxial dull or lustrous, glabrous, rarely pubescent, eglandular. Inflorescences corymbs, panicles, sometimes solitary, 1–30(–50)-flowered. Pedicels erect or recurved, sometimes curved or reflexed as hips mature, slender or stout, 2–20(–35) mm, glabrous or pubescent, eglandular or usually stipitate-, rarely sessile- or setose-glandular; bracts persistent, 1–3, margins entire or serrate, sometimes undulate. Flowers 1–9 cm diam.; hypanthium globose to depressed-globose, ovoid, or ovoid-urceolate, sometimes cupulate, oblong, or hemispheric, glabrous or sparsely hairy, eglandular, stipitate-, or setose-glandular; sepals persistent or deciduous, erect, spreading, or reflexed, rarely ascending, lanceolate or ovate-lanceolate, 5–30(–40) × 1.5–6 mm, margins entire or pinnatifid, abaxial surfaces glabrous, rarely pubescent, sessile-, stipitate-, or setose-glandular, sometimes eglandular; petals single or double, pink to rose or purplish pink, rarely white or crimson; carpels (3–)20–40(–65), styles free exsert (0.5–)1–2.5(–4) mm, pilose, stylar orifice 1–3 mm diam., hypanthial disc flat, 2–5(–10) mm diam. Hips scarlet or red to orange-red, rarely purplish, brownish, or crimson or blue-purple, globose to depressed-globose, ovoid, obovoid, or ellipsoid, rarely pyriform, urceolate, elongate, or oblong, 6–18(–24) × 5–15(–25) mm, glabrous, sometime setose, eglandular or stipitate-, rarely setose-, glandular; sepals persistent or deciduous, erect, reflexed, or spreading. Achenes basal or basiparietal.

Distribution

North America, Mexico, Eurasia, introduced in Pacific Islands (New Zealand), Australia.

Discussion

Species ca. 50 (19 in the flora).

Molecular phylogenetic and multivariate analyses of Rosa (S. Joly et al. 2006; Joly and A. Bruneau 2006, 2007; Bruneau et al. 2007) determined that certain eastern diploid species form a clade distinct from more western diploids; that R. arkansana is derived from the R. blanda–R. woodsii group; that R. carolina is likely of hybrid origin from one of the latter groups and R. palustris; that R. virginiana is derived either from R. nitida, R. palustris, or a hybrid between the two; and that the three polyploid species, R. arkansana, R. carolina, and R. virginiana, evolved multiple times.

Rosa ×dulcissima Lunell (R. blanda × R. woodsii) (W. H. Lewis 1962) occurs in Manitoba, southeastern Saskatchewan, Minnesota, North Dakota, South Dakota, and Wisconsin. In its Manitoba epicenter, B. Ziola and J. R. Dugle (1970) recognized numbers of the hybrid in excess of either parent. However, the validity of the hybrid has been questioned, as has the distinctiveness of R. woodsii from R. blanda (S. Joly and A. Bruneau 2007). The two species and their hybrid are retained here based on morphological and ecogeographic distinctions.

Rosa collaris Rydberg (2n = 14, diploid) (D. Zlesak and W. H. Lewis, unpubl.) probably represents the hybrid between R. gymnocarpa and R. woodsii subsp. ultramontana. Plants annotated with this name differ from the former in having more persistent sepals and/or hairy leaflets with eglandular teeth, and from the latter in having solitary flowers, small hips, or other features more characteristic of R. gymnocarpa.

Selected References

Joly, S. and A. Bruneau. 2007. Delimiting species boundaries in Rosa sect. Cinnamomeae (Rosaceae) in eastern North America. Syst. Bot. 32: 819–836.

Lower Taxa

Rosa acicularis, Rosa arkansana, Rosa blanda, Rosa bridgesii, Rosa californica, Rosa carolina, Rosa cinnamomea, Rosa foliolosa, Rosa glauca, Rosa gymnocarpa, Rosa nitida, Rosa nutkana, Rosa palustris, Rosa pinetorum, Rosa pisocarpa, Rosa rugosa, Rosa spithamea, Rosa virginiana, Rosa woodsii

Key

1	Distal branches usually unarmed, rarely with prickles and aciculi, glabrous	> 2
1	Distal branches armed, usually glabrous, rarely tomentose or puberulent (in R. rugosa)	> 5
2	Stems sparsely branched; stamens 115 (unknown in R. glauca); stylar orifices 1.5–2 mm diam.; e Rocky Mountains to e North America	> 3
2	Stems densely or openly branched; stamens 65–100; stylar orifices 2–2.5 mm diam.; w North America from Cascades to w Rocky Mountains	> 4
3	Stipules 1.5–2 mm wide; pedicels stipitate-glandular; flowers 2–3 cm diam.; leaflets abaxially glaucous, pale green, sometimes dull red, adaxially green-red or purplish, glaucous.	Rosa glauca
3	Stipules 4–6 mm wide; pedicels eglandular, rarely sparsely stipitate-glandular; flowers 3–6(–7) cm diam.; leaflets abaxially not glaucous, abaxially pale green, adaxially green, dull to ± lustrous.	Rosa blanda
4	Inflorescences (1–)3–10(–25+)-flowered, usually panicles; sepals 8–15(–21) × 1.5–2.5 mm; hypanthia 3–5 mm diam., necks 1.5–3.5 mm diam.; usually in full sun near water, centered in Great Basin and Columbia Plateau.	Rosa woodsii
4	Inflorescences 1–3(–9)-flowered, corymbs; sepals 14–25(–35) × (2–)3–4 mm; hypanthia 5–8.5 mm diam., necks 3–6 mm diam.; forested areas, from Cascades to Rocky Mountains, skirting Great Basin.	Rosa nutkana
5	Distal branches without or with relatively few infrastipular prickles, usually with mixed internodal prickles and aciculi	> 6
5	Distal branches with paired, sometimes single, infrastipular prickles (rare in R. nitida), with or without internodal prickles and aciculi	> 8
6	Sepals deciduous; hips irregularly ellipsoid or ellipsoid to nearly globose; terminal leaflet margins 2- or multi-serrate, teeth 7–13 per side; flowers 1.5–3 cm diam., stylar orifices 1 mm diam.; carpels 3–12(–16).	Rosa gymnocarpa
6	Sepals persistent; hips subglobose, globose, ellipsoid, oblong, or urceolate; terminal leaflet margins 1-serrate or 1-, 2-, or multi-dentate-serrate, teeth 8–25 per side; flowers 3–6 cm diam., stylar orifices 1.5–2 mm diam.; carpels 18–33 or 26–43	> 7
7	Inflorescences 1–6(–16)-flowered on current year stems; leaflets (5–)7–9(–11), contiguous, terminal blade margins serrate, teeth 8–16 per side; pedicels erect.	Rosa arkansana
7	Inflorescences 1 or 2(or 3)-flowered on current and older stems; leaflets 5–7, not contiguous, terminal blade margins dentate-serrate, teeth 11–25 per side; pedicels reflexed (as hips mature).	Rosa acicularis
8	Prickle bases pubescent; flowers 6–9 cm diam.; leaflets abaxially deeply veined, adaxially rugose (rarely smooth in R. ×hollandica); hypanthial discs 5–10 mm diam.	Rosa rugosa
8	Prickle bases glabrous; flowers (1–)2.5–5.5(–9) cm diam.; leaflets not deeply veined or rugose; hypanthial discs (2–)3–5 mm diam	> 9
9	Sepals deciduous as hips mature, usually reflexed or widely spreading after anthesis; pedicels and hypanthia stipitate-glandular, rarely eglandular; achenes mostly basal, rarely basiparietal (in R. virginiana)	> 10
9	Sepals persistent as hips mature, usually erect or ± spreading after anthesis; pedicels and hypanthia eglandular, sometimes stipitate-glandular (in R. spithamea, R. nutkana); achenes mostly basiparietal, rarely basal (in R. cinnamomea)	> 14
10	Distal branches: internodal prickles (red to reddish purple) mixed with aciculi, infrastipular prickles rare or absent; stems usually procumbent (sometimes relatively short).	Rosa nitida
10	Distal branches: internodal prickles and aciculi rare or absent, infrastipular prickles not mixed with aciculi; stems erect, sometimes spreading	> 11
11	Terminal leaflet margins 1–2-serrulate, teeth 20–30 per side; auricles erect, rarely flared; swamps and wetlands.	Rosa palustris
11	Terminal leaflet margins serrate, teeth 8–18(–23) per side; auricles flared; rarely swamps or wetlands	> 12
12	Pedicels 2–8 mm; petals white, rarely pink; terminal blades 3–7 mm wide; hips leathery; mostly Oklahoma, n Texas.	Rosa foliolosa
12	Pedicels 5–19(–25) mm; petals pink to deep rose, rarely white; terminal blades 6–28 mm wide; hips fleshy; mostly e North America, rarely e Texas	> 13
13	Leaflets adaxially lustrous; stipules 4–9 mm wide; sepals 20–40 mm; stems erect, stout; infrastipular prickles stout, erect, curved, or declined, rarely hooked, bases relatively broad.	Rosa virginiana
13	Leaflets adaxially dull, rarely slightly lustrous; stipules 2–3 mm wide; sepals 10–22 mm; stems spreading, weak, sometimes erect; infrastipular prickles subulate, erect, sometimes declined, rarely curved, bases relatively narrow.	Rosa carolina
14	Subshrubs, forming open colonies; stems 1–8(–15) dm; California, Oregon	> 15
14	Shrubs, loosely clustered, or forming thickets; stems 2–25(–50) dm	> 17
15	Hypanthia stipitate- to setose-glandular, very rarely eglandular.	Rosa spithamea
15	Hypanthia eglandular	> 16
16	Hypanthia ovoid to depressed-globose; infrastipular prickles single or paired, internodal prickles and aciculi dense; inflorescences 1–5(+)-flowered; coastal.	Rosa pinetorum
16	Hypanthia ovoid-globose to widely urceolate; infrastipular prickles paired, internodal prickles and aciculi rarely present; inflorescences 1 or 2(–7)-flowered; Sierra Nevada and Cascade mountains.	Rosa bridgesii
17	Leaflets abaxially ± glaucous; petals double, rarely single; stipules often convolute; achenes basal; introduced.	Rosa cinnamomea
17	Leaflets abaxially usually not glaucous; petals single; stipules not convolute; achenes basiparietal; native	> 18
18	Inflorescences 1–3(–9)-flowered, corymbs; petals (15–)20–32 mm; sepals 14–25(–35) mm, tips 5–10(–20) × 1–3 mm; hypanthia 5–8.5 mm diam., necks 3–6 mm diam.; hypanthial discs 5 mm diam.; hips 10–20(+) mm diam	Rosa nutkana
18	Inflorescences 1–30(–50)-flowered, panicles or corymbs; petals (10–)15–20(–25) mm; sepals 8–17(–21) mm, tips 1–7(–10) × 0.3–2.5 mm; hypanthia 2.5–5.5 mm diam., necks 1.5–4.5 mm diam.; hypanthial discs 3–4(–5) mm diam.; hips 5–15(–20) mm diam	> 19
19	Petioles and rachises usually puberulent-velutinous, hairs 0.1(–0.5) mm; terminal leaflet blades usually widest at or above middle, teeth (5–)7–14 per side on distal 1/2+ of margin; internodal prickles usually sparse to dense (except subsp. ultramontana); mostly e of Sierra-Cascade axis.	Rosa woodsii
19	Petioles and rachises glabrous or hairy, hairs to 1 mm; terminal leaflet blades usually widest at or below middle, teeth 7–22 per side on distal 3/4+ of margin; internodal prickles absent or rare; mostly Sierra-Cascade axis and west	> 20
20	Infrastipular prickles erect, rarely curved, usually subulate, 2–10 × 2–4 mm; sepals abaxially stipitate-glandular (except subsp. ahartii); pedicels usually glabrous, sometimes finely pubescent; hypanthia 2.5–3.5 mm diam., necks 2 mm diam.	Rosa pisocarpa
20	Infrastipular prickles strongly curved to nearly erect, ± flattened, stout, subulate, 3–15(–20) × 2.5–8 mm (to 10–15 mm); sepals usually abaxially eglandular; pedicels hairy, rarely glabrous; hypanthia 3–5.5 mm diam., necks 2–4.5 mm diam.	Rosa californica