Annuals, 5-60 cm. Stems 1-5+, ± erect, branched distally, sparsely leafy, glabrous. Cauline leaves: proximal obovate, pinnately lobed (lobes 3-5+ pairs, triangular to oblong or linear), not fleshy, ultimate margins entire or dentate, faces glabrous; distal reduced (usually with 2 lobes near bases). Calyculi of 5-8+, ovate to lanceolate bractlets, hyaline margins 0.05-0.2 mm. Involucres ± campanulate, 7-10 × 3-6 mm. Phyllaries 16-20+ in 2-3 series, lanceolate to lance-linear, hyaline margins 0.05-0.1 mm wide, faces glabrous. Receptacles not bristly. Florets 19-70; corollas usually yellow, sometimes white, 6-7 mm; outer ligules exserted 1-2 mm. Cypselae ± cylindro-fusiform, 1.7-2.3 mm, ribs extending to ca. 0.1-0.2 mm short of apices (minutely hirtellous or muriculate), ± equal (distal 0.1-0.2 mm of cypselae smooth); pappi persistent, of 8-15+, needlelike teeth plus 1(-2) bristles. Pollen 70-100% 4-porate. 2n = 28.
Flowering Mar-Jun. Gravelly soils beneath shrubs, along ditches, near streams, in sagebrush steppes, creosote bush scrublands; 300-1300 m; Ariz., Calif., Nev., N.Mex.; Mexico (Sonora).
Malacothrix stebbinsii grows in the Mojave Desert (Borrego area, California) and the Sonoran Desert (Santa Catalina, Mazatzal, Baboquivari, and Santa Rita mountains, and elsewhere in Arizona).
FNA 2006, Kearney and Peebles 1969, McDougall 1973
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Herbaceous annuals, to 50 cm tall, stems 1-5, slender, usually branching from the base, glabrous, leafy, with milky sap. Leaves: Mostly basal, to 10 cm long, proximal oblanceolate to lance-linear, sometimes pinnately lobed, the lobes up to 3 mm wide, not fleshy, ultimate margins usually dentate, faces glabrous, becoming alternate and reduced apically, the margins 2-4-dentate near the bases or entire. Flowers: Heads small, radiate, rays yellow, inconspicuous, the outer rays exserted 1-2 mm, receptacles not chaffy, involucres 6-7 mm high, small bracts around the calyx, of 5-12, lance-deltate to lanceolate bractlets, phyllaries subequal, 8-15 or more in 2 or more series, these lance-linear to linear, the abaxial faces glabrous, inflorescences with many heads borne in terminal panicles. Fruits: Achenes oblong-linear, truncate, ribbed, crowned with a ring of minute teeth. Pappus of soft bristles, 1-2 of them stiffer and persistent, the remainder deciduous more or less in a ring. Ecology: Found along streams, in cleared areas, burns, slides, chaparral, and creosote bush shrub from 2,500-4,500 ft (762-1372 m); flowering March-June. Distribution: Arizona, California, Nevada, New Mexico; Mexico. Ethnobotany: Unknown Etymology: Malacothrix is from malakos, soft and thrix, hair, while stebbinsii is named for George Ledyard Stebbins Jr. (1906-2000) an American geneticist and evolutionary biologist. Synonyms: Malacothrix clevelandii var. stebbinsii Editor: LCrumbacher 2011