Rhamnus crocea
Rhamnus cathartica
hollyleaf buckthorn, redberry, redberry buckthorn, spiny redberry
common buckthorn, European buckthorn, nerprun cathartique
reddish to red-purple or orange-brown; glabrous.
dark to reddish gray or purple, glabrous.
persistent, alternate;
petiole 2–6 mm;
blade usually dull green abaxially, shiny dark green adaxially, elliptic to obovate or ovate, 0.7–2 cm, distinctly coriaceous, base cuneate to truncate, margins coarsely serrate, spinulose-serrulate, or entire, apex obtuse to emarginate, both surfaces glabrous;
secondary veins 5–7 pairs, all diverging at nearly same angle.
deciduous (often present well after frost), usually opposite to subopposite, rarely alternate, sometimes fascicled on short shoots;
petiole 10–27 mm;
blade dull green abaxially, glossy darker green adaxially, usually ovate to elliptic-ovate, sometimes broadly elliptic or nearly orbiculate, (2–)4–7 cm, usually 1–2 times longer than wide, herbaceous, base rounded to rounded-truncate or slightly subcordate, margins crenate-serrate, apex acute to rounded, often abruptly short-acuminate, both surfaces glabrous;
secondary veins 2–4 pairs, all diverging at nearly same angle or proximal diverging more obtusely.
fascicles or flowers solitary.
fascicles or flowers solitary.
2–3 mm.
2–4 mm.
red, globose, 5–8 mm;
stones 2.
black, globose to depressed-globose, 5–6(–8) mm;
stones 3–4.
4(–5).
4.
0.
4.
= 24.
Rhamnus crocea
Rhamnus cathartica
Rhamnus crocea and closely related species were considered conspecific by C. B. Wolf (1938), who treated those in the flora area as subspp. crocea, ilicifolia, pilosa, and pirifolia; he also recognized subsp. insula (Kellogg) C. B. Wolf from Mexico (Baja California). The taxa are distinctive, but intermediates exist. Wolf identified R. crocea/ilicifolia intermediates from Marin County to the California/Mexico boundary, and R. ilicifolia/insula, R. crocea/pilosa, and R. ilicifolia/pilosa intermediates in southern California, especially in San Diego County.
Arizona plants (Pima County, especially in the Ajo Mountains) identified as Rhamnus crocea (for example, K. Christie 2006) appear to be populational variants of the single species present there, R. ilicifolia (R. Felger, pers. comm.). In California, where the two are sympatric over a relatively broad region, R. crocea is distinct from R. ilicifolia in usually bearing thorns and in having smaller leaves with less spinulose margins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Rhamnus cathartica was introduced to North America as an ornamental shrub in the middle 1800s and was originally used for hedges, farm shelterbelts, and wildlife habitat; it is an aggressive invader of woods and prairies and is able to completely displace native vegetation. W. H. Brewer collected R. cathartica (UC 18526) in the 1800s from an unknown location in California. No specimens have been collected in the state since that time and it apparently is not naturalized there.
Rhamnus cathartica is a primary host for the soybean aphid, Aphis glycines, native to eastern Asia. It uses the buckthorn as a winter host and spreads to soybean in the spring. The insect was first discovered in North America in 2000 in Wisconsin and subsequently has spread to at least 20 states in the United States and three provinces in Canada. The orange-colored wood of R. cathartica is sometimes used by woodcarvers.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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