Subshrubs, 20-60(-80) cm. Stems branched mostly in proximal ³ / 4 , ± piloso-villous, stipitate-glandular. Leaf blades lanceolate to elliptic-oblong or oblanceolate, 3-20(-25) mm wide, bases often subclasping or sometimes attenuate and not clasping, margins flat, sharply spinulose-toothed, faces loosely villous or glabrous, stipitate-glandular. Peduncles 5-25 cm. Involucres 12-20 × 15-20(-30) mm. Ray florets (15-)18-60(-85); corollas usually lavender, seldom white. Style-branch appendages shorter than stigmatic lines.

Duration: Perennial

Nativity: Native

Lifeform: Subshrub

General: Perennial herbs to subshrubs, 20-80 cm tall, from a much-branched caudex; stems branched near the base and middle of the plant but not near stem tips; herbage stipitate-glandular and often villous as well.

Leaves: Alternate and sessile; blades linear or lanceolate to oblanceolate, 2-10 cm long and 3-25 mm wide, the bases often subclasping or sometimes attenuate and not clasping, margins with sharp spine-tipped teeth, faces stipitate-glandular, sometimes also loosely villous.

Flowers: Flower heads purple and yellow, radiate, solitary on 5-25 cm peduncles; involucre (ring of bracts wrapped around flower head) campanulate to hemispheric, 1-2 cm high, the bracts (phyllaries) 25-45, graduated in 3-6 series, narrowly lanceolate; ray florets 15-85, the corolla laminae (ray petals) lavender or occasionally white, 1-3 cm long; disc florets 70-110, the corollas yellow, 6-8 mm long.

Fruits: Achenes 3-6 mm long, sericeous, topped with a persistent pappus of tawny, unequal-length barbellate bristles up to 9 mm long.

Ecology: Found on sandy or gravelly slopes and flats, often over clay, alkaline, barren areas, in creosote bush, sagebrush, shadscale, blackbrush, and juniper communities, below 6,500 ft (1981 m); flowers March-June.

Distribution: AZ, CA, NV, UT

Notes: The genus Xylorhiza, formerly placed within Machaeranthera, is distinguished as being perennial herbs, subshrubs, and shrubs from large, woody taproots with woody, branched, persistent caudices; with large, solitary radiate flower heads; long phyllaries in several graduated series, with erect or spreading apices; white or bluish ray flowers; large achenes; and flowering in the spring. X. tortifolia is distinguished by being a perennial herb to subshrub; with stems branched only in the lower 1/2 to 3/4 of the plants; leaves with spine-tipped teeth, the bases of the leaves often clasping the stem; and herbage covered with gland-tipped hairs. There are 2 varieties; X. tortifolia var. tortifolia has stems, leaves and phyllaries that are piloso-villous to puberulent and finely stipitate-glandular; X. tortifolia var. imberbis has stems, leaves and phyllaries that have stipitate glands but are otherwise glabrous.

Ethnobotany: Unknown

Etymology: Xylorhiza from the Greek xylon, wood, and rhiza, root; tortifolia means twisted leaves.

Synonyms: Haplopappus tortifolius, Aster tortifolius, Machaeranthera tortifolia

Editor: AHazelton 2015