Desert hoary coffeeberry Desert hoary coffeeberry

Rhamnus ursina Greene, Leafl. Bot. Observ. Crit. 1: 63. 1904; Frangula ursina (Greene) Grubov; R. californica Eschscholtz subsp. ursina (Greene) C. B. Wolf; R. californica var. ursina (Greene) McMinn; R. castorea Greene; R. tomentella Bentham subsp. ursina (Greene) J. O. Sawyer

Leaf blades green adaxially, elliptic to ovate, 3–8.5 cm, margins entire to serrulate or serrate with gland-tipped teeth, flat to slightly revolute, apex acute to rounded, abaxial surface densely and closely white stellate-hairy, usually with simple, erect hairs at least along veins (sometimes relatively inconspicuous), adaxial surface nearly glabrous; veins not prominent abaxially. Drupe stones 2.

Flowering May–Sep. Chaparral, desert scrub, woodlands; 700–2600 m; Ariz., Calif., Nev., N.Mex.; Mexico (Sonora).

C. B. Wolf (1938) considered a collection from Cochise County in southeastern Arizona named as Rhamnus blumeri Greene [Frangula ×blumeri (Greene) Kartesz & Gandhi] to be a hybrid between Frangula californica var. ursina and F. betulifolia. Study of an isotype of R. blumeri, and specimens of Wolf 2592 (MO), 2593 (MO), 2595 (MO), and Wolf & Everett 11384 (TEX), essentially corroborate the observations by Wolf. However, from examination of numerous other collections of both species from the Chiricahua Mountains, it appears that hybridization between F. betulifolia and F. californica is not common.