Draba petrophila


Pittonia 4: 17. 1899.

Synonyms: Draba helleriana var. blumeri C. L. Hitchcock Draba helleriana var. petrophila (Greene) O. E. Schulz
Treatment appears in FNA Volume 7. Treatment on page 329. Mentioned on page 278, 330, 345.

Perennials; (cespitose, long-lived); caudex simple or branched (covered with persistent petioles), not scapose. Stems usually unbranched, rarely branched, 0.3–1.9(–2.8) dm, moderately to densely hirsute throughout, trichomes simple, 0.2–1.3 mm, with short-stalked to subsessile, cruciform, 0.02–0.4 mm, and 2-rayed ones, 0.3–0.9 mm. Basal leaves rosulate; petiolate; petiole ciliate, (trichomes simple, 0.4–1.5 mm); blade oblanceolate, 1–5(–6) cm × 2–5(–10) mm, margins usually entire, rarely denticulate, surfaces pubescent, abaxially with stalked, cruciform trichomes, 0.07–0.5 mm, adaxially often similar, sometimes with fewer, simple and 2-rayed trichomes, 0.4–1.3 mm. Cauline leaves 3–10; sessile; blade ovate to lanceolate or oblong, margins entire or denticulate, surfaces pubescent as basal. Racemes 10–37(–58)-flowered, ebracteate, elongated in fruit; rachis not flexuous, pubescent as stem. Fruiting pedicels divaricate-ascending, straight, 4–10 mm, pubescent throughout, trichomes simple (0.1–0.5 mm) and subsessile, 2–4-rayed, (0.03–0.2 mm). Flowers: sepals oblong, 2–3.5 mm, pubescent, (trichomes simple and 2-rayed); petals yellow, oblanceolate, 3.5–6 × 1.2–1.8 mm; anthers oblong, 0.8–1 mm. Fruits lanceolate to elliptic, often strongly twisted, flattened, 5–11 × 2–3 mm; valves puberulent at least along margin, trichomes simple, antrorse, 0.03–0.15 mm; ovules 14–24 per ovary; style 0.8–1.8(–2.5) mm. Seeds ovoid, 1–1.4 × 0.6–0.9 mm.

Phenology: Flowering Jul–Sep.
Habitat: Crevices, ledges of cliffs
Elevation: 1200-2800 m


Draba petrophila is often broadly circumscribed to include the taxon herein called D. viridis. For a discussion of the differences between these species and the closely related D. helleriana, see I. A. Al-Shehbaz and M. D. Windham (2007). Draba petrophila, in the strict sense, is known only from Cochise, Pima, and Santa Cruz counties in southeastern Arizona.

Selected References


Lower Taxa