KEY TO ROSA
1. Stipules deeply fringed or comb-like; inflorescence multiflowered..........R. multiflora
1. Stipules entire to coarsely toothed; inflorescence single to several-flowered.
1a. Prickles strongly curved, stout; calyx-lobes often with conspicuous lateral segments and usually reflexed after flowering.
2. Lower surface of leaflets stalked-glandular..............R. eglanteria
2. Lower surface of leaves not stalked-glandular (sometimes a few glands along leaf axis or midrib of leaflets)..................R. canina
1a. Prickles not or slightly curved, often slender; calyx-lobes usually without lateral segments, usually ascending or erect after flowering.
3. Calyx-lobes deciduous in fruit, 12 mm long or less; petals 15 mm long or less...............R. gymnocarpa
3. Calyx-lobes persistent in fruit, greater than 12 mm long; petals greater than 15 mm long.
4. Stems with well-defined infrastipular prickles (pair of prickles at or just below each node) or nearly unarmed.
5. Calyx-lobes usually glandular-bristly; leaflets finely toothed; plants from west of the Coast-Cascade Mountains............R. pisocarpa
5. Calyx-lobes usually not glandular-bristly; leaflets coarsely toothed.
6. Flowers small and clustered; calyx-lobes mostly 1-2 cm long and 2-3.5 mm wide at base; petals 1.2-2.5 cm long................R. woodsii
6. Flowers large and usually solitary; calyx-lobes mostly 1.5-4 cm long and 3-6 mm wide at base; petals 2.5-4 cm long.....................R. nutkana
4. Stems more or less bristly with slender prickles; infrastipular prickles, if any, like the others.
7. Flowers mostly solitary, usually on lateral branchlets of current season; leaflets usually 5 to 7 (9); petals more than 2 cm long..................R. acicularis
7. Flowers commonly clustered at ends of main shoots of current season as well as on lateral branchlets; leaflets (7) 9-11; petals less than 2.5 cm long..............R. arkansana
Source: Illustrated Flora of British Columbia (Vol. 4). (1999)
 (edited) nr.jpg)
