Cliff rose

Cowania stansburyana Torrey in H. Stansbury, Exped. Great Salt Lake, 386, plate 3. 1852 (as stansburiana); C. mexicana D. Don var. stansburyana (Torrey) Jepson; Purshia mexicana (D. Don) S. L. Welsh var. stansburyana (Torrey) S. L. Welsh

Shrubs, evergreen, 10–40(–75) dm. Stems: young-stem internodes 5–14 mm, sparsely hirtellous or glabrous, usually stipitate-glandular; short-shoot spurs simple or branched, 10–20(–40) × 1.2–2.7 mm. Leaves: blade dark green adaxially, obovate, (3–)7–12(–19) × (2–)3–8(–13) mm, irregularly lobed in distal 1/2, lobes (3–)5(–7), proximal 2 lobes ascending, oblong to spatulate, ˂narrow, 2–6 mm˃, distal 3 lobes deflexed, reduced, margins strongly revolute, usually entire, rarely toothed proximally, ˂apex rounded to truncate˃, abaxial surface white-villous, midvein ˂greenish˃, glabrate, ˂glandular-punctate˃, adaxial sparsely hirtellous or arachnoid villous, soon glabrate, ± glandular-punctate. Pedicels 2.5–4.5 mm. Flowers: hypanthium obconic, 4–6.5 × 1.5–3 mm, 3–5 mm diam. in fruit, arachnoid-villous to pubescent, usually stipitate-glandular; petals light to cream-yellow or -white, broadly obovate, 7–13(–15) mm; stamens (52–)60–90(–125); carpels (3–)4–7(–10). Achenes oblanceoloid, 6–8 × 1.8–2.2 mm, 12-ribbed, persistent style 35–59 mm, plumose hairs 1.4–2.2 mm. 2n = 18.

Flowering Apr–May(–Oct). Pinyon-juniper, Joshua tree, yellow pine woodlands, arid desert scrub, desert chaparral; (1000–)1200–2200(–2600 m); Ariz., Calif., Colo., Idaho, Nev., N.Mex., Utah; Mexico (Baja California, Sonora).

Purshia stansburyana is vegetatively similar to P. tridentata var. glandulosa, the latter usually having thicker leaves with narrower abaxial grooves and apiculate apices. The two sometimes can only be distinguished by flowers or fruits.

Purshia stansburyana forms hybrids with P. tridentata vars. glandulosa and tridentata. The hybrids easily can be recognized by their 2–3(–5) carpels and achenes with styles 12–28 mm, among other characteristics (H. C. Stutz and L. K. Thomas 1963). Hybrids between P. stansburyana and P. tridentata var. glandulosa have been given the names Cowania mexicana var. dubia Brandegee and C. alba Goodding. Introgression with P. stansburyana occurs in two populations of P. subintegra.