Key to Rosa

View taxon page for Rosa

(For a list of species in Rosa, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Leaflets << 1 cm, toothed ± 1/2 to base; 

hypanthium 

Structure generally in the shape of a tube, cup, or bowl, derived from the fused lower portions of the perianth and stamens, from which these parts seem to arise, and to which the ovary wall is fused in an inferior ovary (to which the ovary wall is partially fused in a half-inferior ovary; from which the ovary is free in a superior ovary).

densely prickly – PR ..... R. minutifolia

1' Leaflets generally > 1 cm, toothed < 1/4 to base; hypanthium glabrous to stalked-glandular

2. Sepals with toothed lateral 

lobes 

1. A major expansion or bulge, such as on the margin of a leaf, sepal, or petal, or on the surface of an ovary. 2. The free tips of otherwise fused structures, such as sepals or petals; larger than teeth.

; prickles 

compressed 

Flattened side-to-side or front-to-back.

side-to-side, curved

3. Hypanthium 1–2 mm wide at flower, 5–7 mm wide at fruit; pistils generally < 10 ..... R. multiflora

3' Hypanthium 4–5 mm wide at flower, 10–20 mm wide at fruit; pistils > 10

4. Leaves and sepals ± glandless; petals white to pink; terminal 

leaflet 

A leaf-like unit of a compound leaf; distinguished from a leaf by the absence in its axil of a bud, branch, thorn, or flower; lacking lateral, basal appendages (stipules); either simple (leaf 1-compound, with primary leaflets) or compound (leaf 2-compound, with primary and secondary leaflets; 3-compound, with primary, secondary, and tertiary leaflets, etc).

± 

ovate 

Egg-shaped (i.e., widest below the middle) in two dimensions (i.e., in one plane), as a leaf.

..... R. canina

4' Leaves and sepals glandular; petals pink; terminal leaflet generally 

elliptic 

In the shape of a flattened circle or ellipse; wider than linear

to ± widely obovate ..... R. rubiginosa

2' Sepals generally 

entire 

Having margins that are continuous and smooth (i.e., without teeth, lobes, etc.).

(tip sometimes toothed); prickles compressed or slender, straight or curved

5. Sepals deciduous in fruit; hypanthium 1.5–2 mm wide at flower; pistils 5–10; sepal tip generally << body; petals ± 10 mm – leaflets glabrous, flowers 1–3; 

pedicels 

Stalk of an individual flower in an inflorescence, or the corresponding structure in fruit.

generally stalked-glandular ..... R. gymnocarpa

6. Leaflets generally (5)7–9; terminal leaflet tip generally ± 

obtuse 

Having a short-tapered, blunt tip or base, the sides convex or straight and converging at more than a right angle.

, ± 10–30 mm; pedicels ± 15–30 mm; plants to ± 5–20 dm, generally in shade on non-ultramafic substrates; widespread ..... var. gymnocarpa

6' Leaflets generally 5(7); terminal leaflet tip widely obtuse to rounded, 4–20 mm; pedicels ± 10–15 mm; plants to generally 3–6 dm, full sun on ultramafic substrates; KR ..... var. serpentina

5' Sepals persistent; hypanthium 2.5–7 mm wide at flower; pistils generally > 10; sepal tip ± = or often > body; petals 10–25 mm

7. Dwarf, openly rhizomed shrubs, generally 1–5(10) dm; leaflet tip often ± 

truncate 

Abruptly (not gradually) narrower or smaller at base or tip, as if cut straight across or nearly so.

– 

leaf 

Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets).

 margins generally ± glandular, generally double-toothed

8. Hypanthium stalked-glandular – prickles generally ± slender, often many; NW, CW, MP(1 site), 150–1550(1950) m ..... R. spithamea

8' Hypanthium generally glandless, rarely sparsely glandular

9. Prickles few, paired, ± thick-based; terminal leaflet generally widely obovate; flower 1–2(7); CaR, SN, 700–2500 m ..... R. bridgesii

9' Prickles generally many, generally not paired, both slender and ± thick-based; terminal leaflet generally ± elliptic; flowers generally 1–5; CW, generally < 300 m ..... R. pinetorum

7' Open or thicket-forming shrubs, generally > 5 dm; leaflet tip not truncate

10. Terminal leaflet ± obovate-elliptic, widest at or above middle; leaf axis finely velvety, hairs ± 0.1 mm (glabrous), glandless; prickles slender to ± thick-based, generally ± straight; sepals glandless (in California); CaRH, SNH, Teh, TR, GB, DMtns ..... R. woodsii

11. Prickles generally many, 2–10(13) mm, often ± thick-based, internodal prickles generally present in inflorescence; c&s SNH, Teh, TR, SNE, DMtns, s DMoj exc DMtns (Box S Springs, Cushenbury Springs) ..... subsp. gratissima

12. Leaf axis finely velvety; c&s SNH, Teh, TR, SNE, DMtns ..... var. gratissima

12' Leaf axis glabrous; s DMoj exc DMtn (Box S Springs, Cushenbury Springs) ..... var. glabrata

11' Prickles few to many, 2–7 mm, slender, internodal prickles generally 0 in inflorescence; CaRH, n SNH, MP, n SNE ..... subsp. ultramontana

10' Terminal leaflet generally ovate to elliptic, generally widest at or below middle; leaf axis variously hairy, hairs to 1 mm, sometimes glandular; prickles generally ± thick-based, often curved; sepals often glandular; CA-FP, adjacent DMoj

13. Flowers generally 1(6); hypanthium generally 5–7 mm wide at flower, (10)13–20 mm wide at fruit, generally ± spheric; achenes generally 4.5–6 mm – prickles to 20 mm, generally ± compressed, ± straight to ± curved; sepal tips generally > body, toothed ..... R. nutkana

14. Leaflets generally ± single-toothed, generally glandless; prickles generally few; NCoRO, KR, CaRH; 750–1500 m ..... subsp. macdougalii

14' Leaflets double-toothed, ± glandular especially beneath; prickles generally many; NCo, NCoRO, CCo; < 700 m ..... subsp. nutkana

13' Flowers 1–many; hypanthium 2.5–5.5 mm wide at flower, 7–15(20) mm wide at fruit, spheric to (ob)ovoid; achenes 3–5 mm

15. Prickles generally thick-based, generally curved (straight), few to many; leaflets and leaf axis generally ± shaggy-hairy, hairs to 1 mm; 

pedicel 

Stalk of an individual flower in an inflorescence, or the corresponding structure in fruit.

generally ± hairy; hypanthium generally (ob)ovoid, glabrous to sparsely hairy, neck 2–4.5 mm wide at flower ..... R. californica

15' Prickles slender to ± thick-based, straight (± curved), 0–few; leaflets and leaf axis ± glabrous to ± hairy, hairs 0.1–1 mm; pedicels generally glabrous (except for glands); hypanthium spheric to ovoid, glabrous, neck ± 2 mm wide at flower ..... R. pisocarpa

16. Flowers 1–3(10); sepals generally glandless; prickles 0 to paired at 

nodes 

Position on a stem from which one or more structures (especially leaves, buds, branches, or flowers) arise.

; leaflets generally 5(7) ..... subsp. ahartii

16' Flowers (1)3–10; sepals generally glandular; prickles generally paired at nodes; leaflets generally (5)7(9) ..... subsp. pisocarpa

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