Annuals, 10-35 cm. Stems 1(-9), erect, branched from bases and distally, relatively sparsely leafy, glabrous. Cauline leaves: proximal narrowly oblanceolate to obovate, usually pinnately lobed (lobes oblong to triangular), not fleshy, ultimate margins ± dentate, faces glabrous; distal greatly reduced (margins entire or basally dentate, apices acute). Calyculi of 5-8+, subulate to lanceolate bractlets, hyaline margins 0.05-0.2 mm. Involucres ± campanulate, 6-9 × 4-6.6 mm. Phyllaries 12-15+ in 2(-3) series, lance-oblong to lance-linear, hyaline margins 0.05-0.2 mm wide, faces glabrous. Receptacles not bristly. Florets 30-61; corollas white or pale yellow, 6-10+ mm; outer ligules exserted 1-4 mm. Cypselae ± cylindro-fusiform, 1.7-2 mm, ribs ending 0.2-0.3 mm short of apices, ± equal (distal 0.2-0.3 mm of cypselae slightly expanded, smooth); pappi persistent, of 16-18 needlelike teeth plus 2 bristles. Pollen 70-100% 3-porate. 2. = 14.
Flowering Mar-May. Sandy, open areas among bushes, Larrea-Lycium-Cercidium-Baccharis associations, Quercus, Pinus, Juglans woodlands; 400-1500 m; Ariz., N.Mex.; Mexico (Sonora).
Malacothrix sonorae is found mainly in the Sonoran Desert (Tucson, Kofa, Pinal, White Tank, Baboquivari, and Waterman mountains).
FNA 2006, Kearney and Peebles 1969, McDougall 1973
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Herbaceous annuals, to 50 cm tall, stems 1-9, slender, usually branching from the base and distally, glabrous, sparsely leafy, with milky sap. Leaves: Proximal and cauline; the proximal narrowly oblanceolate to obovate, usually pinnately lobed, the lobes oblong to triangular, the ultimate margins dentate, the faces glabrous; the distal leaves greatly reduced, the margins entire or basally dentate, the apices acute, not fleshy. Flowers: Heads small, numerous, white to pale yellow, radiate, the rays inconspicuous, outer rays exserted 1-4 mm, receptacles not chaffy, the involucres 6-7 mm high, small bracts around the calyx, of 5-8 or more subulate to lanceolate bractlets, phyllaries subequal, of 12-15 or more in 2-3 series, these lance-oblong to lance-linear, equal, glabrous, the inflorescences with many heads borne in terminal panicles. Fruits: Achenes oblong-linear, truncate, ribbed, crowned with a ring of minute teeth. Pappus persistent, of 16-18 needlelike teeth plus 2 bristles. Ecology: Found in sandy, open areas among bushes, Larrea-Lycium-Cercidium-Baccharis associations, and Quercus, Pinus, and Juglans woodlands from 1,500-5,000 ft (457-1524 m); flowering March-May. Distribution: Arizona, New Mexico; Mexico. Ethnobotany: Unknown Etymology: Malacothrix is from malakos, soft and thrix, hair, while sonorae means of or from Sonora, Mexico Synonyms: None Editor: LCrumbacher 2011