Phytoneuron 2015-48: 16, figs. 2, 5, 6A, 7. 2015.
Plants simple, rarely branched, sometimes with several stems from host attachment, 5–35 cm, relatively slender, base not enlarged, glabrous proximally, glandular-pubescent distally. Roots inconspicuous, slender, usually unbranched. Leaves numerous, sometimes imbricate distally, appressed; blade lanceolate to broadly ovate, 4–10 mm, margins entire, apex acute, surfaces glabrous. Inflorescences spikelike racemes, dark purple, sometimes pale lavender, sometimes branched, densely glandular-pubescent, often viscid; flowers numerous; bracts erect to recurved, narrowly oblong-lanceolate, 5–11 mm, apex acute, glandular-pubescent. Pedicels 0–5 mm (15 mm proximally), much shorter than plant axis; bracteoles 2. Flowers: calyx lavender to purple externally, weakly bilaterally symmetric, 8–12(–14) mm, deeply divided into 5 lobes, lobes lanceolate-linear to linear-subulate, densely glandular-pubescent; corolla 15–20(–22) mm, tube white, constricted above ovary, slightly bent forward, glandular-puberulent or pubescent; palatal folds prominent, yellow, villous distally, hairs eglandular; lips dark purple, abaxial lip sometimes lavender, abaxial lip erect to slightly spreading, 3–4 mm, lobes linear, apex acute, adaxial lip erect to ± spreading, 4–6 mm, lobes triangular-acute to narrowly oblong-triangular, apex obtuse-rounded; filaments glabrous or with a few scattered hairs, anthers included, glabrous or sparsely woolly along sutures. Capsules ovoid, 6–10 mm. Seeds 0.3–0.5 mm. 2n = 48.
Phenology: Flowering Jun–Jul.
Habitat: Red sands, high deserts, pinyon-juniper woodlands.
Elevation: 1000–3000 m.
Ariz., Nev., N.Mex., Utah.
Orobanche arizonica is rather common in the high desert of northern Arizona and southern Utah. It is parasitic on Gutierrezia sarothrae (Asteraceae) and possibly other species of the genus.
Orobanche arizonica occurs in the Colorado Plateau and southern Great Basin Desert and contiguous areas. It is often confused with O. ludoviciana or is considered a small-flowered O. cooperi. The smaller flowers, summer flowering period, host, and ecological setting separate it from O. cooperi of the warm Sonoran Desert (L. T. Collins and G. Yatskievych 2015).