Flora of North America species comparison

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Frangula rubra

red buckthorn, Sierra coffee berry
Habit Shrubs, 0.5–2 m. Stems red to gray, glabrous or hairy.
Leaves

deciduous;

petiole 2–12 mm;

blade light to bright green abaxially, green or dull green adaxially, narrowly elliptic to oblong or obovate, 1.5–8.5 cm, ± herbaceous, base rounded to obtuse or acute, margins entire or serrulate to denticulate, apex acute to obtuse or rounded, surfaces glabrous or short-puberulent, or abaxial puberulent on midrib and veins;

secondary veins (7–)8–11 pairs.
Inflorescences

umbels, pedunculate, (2–)4–15-flowered.
Pedicels

1–12 mm.
Drupes

black, globose or pyriform, 8–12 mm;

stones 2(–3).
Stigmas

2-lobed.

Frangula rubra
Distribution
from FNA
CA; NV; OR
[BONAP county map]
Discussion

Subspecies 5 (5 in the flora).

The Frangula rubra complex is a group of closely related populations that needs study. In Nevada, they occur only in Douglas and Washoe counties. Descriptions by C. B. Wolf (1938) provide only a single distinct character to separate the subspecies, and he reported much intergradations between subsp. obtusissima and all the other subspecies. Field and herbarium studies argue for the recognition of infraspecific taxa despite the intermediates.

Subspecies yosemitana and Frangula californica subsp. cuspidata grow along the east side of the Sierra Nevada and can be easily confused. Plants of both taxa can be deciduous, but Wolf noted differences in pubescence and leaf margin to differentiate the two, although both are variable throughout their ranges.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaf blade surfaces short-puberulent.
subsp. yosemitana
1. Leaf blade surfaces glabrous or abaxial puberulent on midrib and veins.
→ 2
2. Young branches gray; leaves clustered on short-shoots.
subsp. modocensis
2. Young branches usually red, rarely gray; leaves scattered along branchlets.
→ 3
3. Leaf blade bases and apices rounded.
subsp. obtusissima
3. Leaf blade bases and apices acute to obtuse.
→ 4
4. Leaf blades bright green; drupes globose.
subsp. rubra
4. Leaf blades usually dull green, especially abaxially; drupes pyriform.
subsp. nevadensis
Source FNA vol. 12, p. 55.
Parent taxa Rhamnaceae > Frangula
Sibling taxa
F. alnus, F. betulifolia, F. californica, F. caroliniana, F. obovata, F. purshiana
Subordinate taxa
F. rubra subsp. modocensis, F. rubra subsp. nevadensis, F. rubra subsp. obtusissima, F. rubra subsp. rubra, F. rubra subsp. yosemitana
Synonyms Rhamnus rubra
Name authority (Greene) Grubov: Trudy Bot. Inst. Akad. Nauk S.S.S.R., Ser. 1, Fl. Sist. Vyssh. Rast. 8: 271. (1949)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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