Plants 30-150 cm. Stems usually 1, erect, sparingly branched, loosely tomentose, sometimes glabrate. Leaves loosely tomentose, soon glabrate; basal petiolate, usually absent at anthesis, smaller than cauline, blades oblanceolate, tapered to base, margins entire or denticulate; cauline sessile, often clasping, usually not much smaller except among heads, blades ovate to lanceolate or oblong, margins entire or serrulate to denticulate; distally reduced to bracts, sometimes appendaged like phyllaries. Involucres broadly hemispheric, 20-35 mm. Phyllaries: bodies stramineous to greenish, ovate (outer) to oblong (inner), appendages erect to spreading, ± brown, fringed with 15-25 slender, ciliate, spinelike teeth 2-4 mm; mid with (9-)10-13(-15) pairs of lobes; faces tomentose or glabrescent. Corollas of neutral florets pink to purple (rarely white), 30-70 mm, enlarged, raylike; of bisexual yellowish, 20-30 mm. Cypselae dark brown, ca. 4 mm, glabrous; pappus bristles unequal, stiff, 5-6 mm.

Flowering Jul-Nov. Damp soil near streams, roadsides, open pine-oak woodlands and forests; 1300-2900 m; Ariz., N.Mex.; Mexico (Chihuahua, Durango, Sinaloa, Sonora).

Plectocephalus rothrockii closely resembles P. americanus. Although the ranges of the two taxa approach each other in southeastern Arizona and adjacent Chihuahua, they are locally allopatric, separated by habitat differences, and are not known to grow together. Plectocephalus americanus is a species of grassland habitats of the southern Great Plains; P. rothrockii is largely restricted to moister canyon sites in the Sierra Madre Occidental of Mexico and associated ranges of the American southwest. Mexican basketflower is sometimes cultivated, and can be expected to occur outside its native range.

Duration: Annual

Nativity: Native

Lifeform: Forb/Herb

General: Herbaceous annuals, to 150 cm tall, stems usually singular, erect, sparingly branched, herbage glabrate to loosely tomentose.

Leaves: Basal leaves oblanceolate, tapered to the base, margins entire or denticulate, tomentose to glabrate, the cauline sessile, often clasping, usually not much smaller except among the heads, blades ovate to lanceolate or oblong, margins entire or serrulate to denticulate, distally reduced to bracts, sometimes appendaged like phyllaries.

Flowers: Heads large, pink to purple or rarely white, of 30-70 neutral florets, these enlarged, raylike; the bisexual florets yellowish, 20-30 mm, the involucres broadly hemispheric, 2-4 cm thick, strongly graduated, phyllaries unarmed, fringed on the terminal appendage, appendages with 8-12 pairs of ciliolate lobes, the undivided portions triangular or ovate.

Fruits: Achenes dark brown, to 4 mm long, glabrous, with an oblique attachment. Pappus of stiff, unequal bristles, 5-6 mm long.

Ecology: Found in damp soil near streams, roadsides, open pine-oak woodlands and forests, from 4,500-9,500 ft (1372-2896 m); flowering July-November.

Distribution: Arizona, New Mexico; Mexico.

Notes: Differentiate from the similar Centaurea americana by the brownish phyllary appendages of P. rothrockii, these have 8-12 pairs of ciliolate lobes, with the undivided portions triangular or ovate; C. americana has 4-6 pairs of non-ciliolate lobes, these whitish, its undivided portions lanceolate.

Ethnobotany: Unknown

Etymology: The meaning of Plectocephalus is unknown, while rothrockii is named for Dr. Joseph Trimble Rothrock (1839-1922), surgeon on the Wheeler expedition of 1873-1875.

Synonyms: Centaurea rothrockii

Editor: LCrumbacher 2011