Plants mostly 15-45 cm. Leaves: basal rosettes not persistent; basal leaves mostly 2-7 × 0.5-2.5 cm; petioles 1-3 cm; blades oblanceolate, often pinnately lobed; cauline leaves gradually reduced distally. Heads borne singly. Peduncles 3-12 cm. Involucres hemispheric, mostly 5-8 × 7-12 mm Phyllaries mostly 21-34, floccose-tomentose. Rays mostly 20-40; laminae elliptic to obovate, mostly 7-10 × 4-7 mm, apices shallowly 3-toothed. Disc florets mostly 40-50; corollas 3 mm, tubes 0.3 mm, lobes 0.25 mm; style-branch apices acute. Cypselae 3 mm. 2n = 32.

Flowering Mar-Nov (depending on rains). Sandy plains and mesas; 100-2000 m; Ariz., Calif., Nev., Utah; Mexico (Baja California, Sonora).

Baileya pleniradiata is superficially similar to B. multiradiata and autumnal forms of the latter have often been misidentified as the former (see discussion under B. multiradiata). The two species occasionally occur together or in proximity; hybrids have not been noted. Style appendages readily allow distinction between the two taxa.

FNA 2006, Wiggins 1964, Kearney and Peebles 1969

Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Annual herb, 15-45 cm tall; stems woolly, loosely ascending, branching from base. Leaves: Basal leaves in rosettes and cauline leaves are alternate; basal leaves early withering, on petioles 1-3 cm long, the blades 2-7 cm long, 0.5-2.5 cm wide, oblanceolate, pinnately lobed; cauline leaves like the basal leaves but reduced upward, becoming sessile, linear to narrowly spatulate, mostly entire. Flowers: Flower heads showy, radiate, terminal, borne singly on peduncles 3-12 cm long; involucre (the ring of bracts surrounding the flower head) hemispheric, 6-8 mm high by 7-12 mm wide, the bracts (phyllaries) 21-34, woolly-tomentose; rays 20-40, corolla laminae (ray petals) yellow, elliptic to obovate, 7-10 mm long, the tips shallowly 3-toothed; disc florets 40-50, corollas yellow, 3 mm high, style branch apices acute. Fruits: Achenes 3-4 mm long, truncate at apex, tapering toward base, distinctly ribbed and angled; lacking pappus. Ecology: Found on sandy soils, on flats and along arroyos below 6,000 ft (1829 m); flowers March-November. Distribution: CA, NV, AZ, UT; south to n MEX (Baja California, Sonora). Some authorities place this species in New Mexico (including many Seinet collections, and Martin and Hutchins' 1980 Flora of New Mexico); however, Allred and Ivey (2012) and Flora of North America (vol. 21; 2006) state that the only Baileya in New Mexico is B. multiradiata. Notes: At first glance this species looks like B. multiradiata, which is the most common of the genus. Pay attention to the fact that this species is an annual, where B. multiradiata is biennial to perennial and often is found in much larger clumps. Also, this species has leaves higher up the stems, sometimes to the apex; shorter peduncles (< 12 cm); and acute style branches. B. multiradiata has leaves concentrated at the bottom of the stems; long peduncles (10-30 cm); and truncate or rounded style branches. According to FNA, "the autumnal blossoms of Baileya multiradiata, with smaller heads, fewer rays, and shorter peduncles, greatly resemble those of B. pleniradiata. This has caused much confusion in the distinction between these two species. The shape of the style apex is a useful character to distinguish between fall-blooming specimens." This may be the source of the confusion as to whether B. pleniradiata grows as far east as New Mexico (see "Distribution" section above). Ethnobotany: Unknown, but other species in the genus have uses. Etymology: Baileya is named for Jacob Whitman Bailey (1811-1857) an early American microscopist, while pleniradiata comes from Latin meaning full-rayed. Synonyms: Baileya multiradiata var. pleniradiata, B. perennis Editor: SBuckley 2010, AHazelton 2015, AHazelton 2017