Frangula alnus
Frangula rubra
alder buckthorn, columnar buckthorn, European alder, European alder-buckthorn, fen buckthorn, glossy buckthorn, glossy false buckthorn, tall hedge buckthorn
red buckthorn, Sierra coffee berry
deciduous;
petiole 10–19 mm;
blade dull green abaxially, glossy darker green adaxially, broadly elliptic-obovate to broadly elliptic or broadly oblong, 4–7(–11) cm, herbaceous, base cuneate to rounded, margins entire, apex rounded to acute or abruptly short-acuminate, abaxial surface sometimes minutely strigose along midveins, adaxial surface glabrous;
secondary veins 6–10 pairs.
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.
fascicles, sessile, 1–8-flowered.
umbels, pedunculate, (2–)4–15-flowered.
3–10 mm.
1–12 mm.
black, globose or slightly elongate, 6–8 mm;
stones 2(–3).
black, globose or pyriform, 8–12 mm;
stones 2(–3).
2–3-lobed.
2-lobed.
= 20–26.
Frangula alnus
Frangula rubra
Two horticultural forms of Frangula alnus are widely sold and planted in North America. The cultivar 'Asplenifolia' (F. alnus var. asplenifolia Dippel; fern leaf or cutleaf buckthorn) has linear-oblong leaves with coarsely toothed to incised margins and commonly is grown as a specialty plant. The cultivar 'Columnaris' (tallhedge glossy buckthorn) has a narrow, upright habit and is used in hedging. Both forms were noted by M. H. Brand (http://www.hort.uconn.edu/plants/r/rhafra/rhafra1.html) to spread invasively by seeds. 'Asplenifolia' has been reported as naturalized in Ontario (A. W. Dugal 1989, 1992), Illinois (A. Branhagen, pers. comm.), and Ohio (M. K. Delong et al. 2005).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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 |
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