Plant: Annual herb; 8-45 cm tall

Leaves: 2-14 cm long, 0.5-4.5 cm wide; petiole 0.5-2.5 cm long; blade lanceolate, the basal ones sometimes elliptic, with 2 (or 4) prominent basal lobes; uppermost sublinear and entire

INFLORESCENCE: cymose

Flowers: sessile; calyx usually persistent; petals orange, 5-7 mm long, 3-4 mm wide, with trichomes at apex only; staminodia 0; outer stamens with very slightly broadened filaments; style 4-5 mm long

Fruit: capsules clavate, long-tapering to base, erect; body 2-3 cm long. SEEDS 8-12, pendulous, not winged, blocky in outline except for the protruding hilum end; testa cells elongate, striate

Misc: Washes, grasslands, canyons, rocky slopes; 1050-1850 m (3500-6000 ft); Aug-Oct

REFERENCES: Christy, Charlotte M. 1998. Loasaceae. J. Ariz. - Nev. Acad. Sci. 30(2): 96.

Duration: Annual

Nativity: Native

Lifeform: Forb/Herb

General: Annual with slender white stems, to 40 cm tall, stems shining, glabrous to pubescent, hairs of the vegetation cause the plant to stick to clothing, although the hairs are not stinging.

Leaves: Blades petiolate, scabrous, thick, the lower leaves narrowly oblanceolate, the margins dentate to entire, the upper leaves linear to lanceolate, 2-3 cm long, pinnatifid.

Flowers: Yellow to bright orange, axillary, sessile, solitary, or in small clusters, sepals to 2 mm long, petals to 4 mm long, stamens shorter than the petals.

Fruits: Linear-cylindric capsules to 16 mm long, seeds square and irregularly angled, seeds grooved on the angles.

Ecology: Found in sandy soils, in washes and on plains; 1,500-6,000 ft (457-1829 m); flowering March-June.

Distribution: Endemic to a small region in se AZ and n MEX.

Notes: The most abundant species of the genus in the very southern portion of AZ. Often found in large patches after the rains in the summer, identified by the hundreds of fruits sticking to pants and socks. Distinctive from other species by being annual with usually one stem from the ground then branching above; stems white; petiolate, lanceolate, toothed leaves with prominent, narrow basal lobes; sessile flowers with orange-yellow petals and linear capsules.

Ethnobotany: There is no specific use of the species recorded, but the genus was used as a food source, the seeds were ground, parbroiled, or parched and stored for later use.

Etymology: Mentzelia is named for Christian Mentzel or Christianus Mentzelius (1622-1701), a 17th century German botanist, while isolata means isolated, referring to this species- geographic isolation from related taxa.

Synonyms: None

Editor: LCrumbacher 2011, FSCoburn 2015