Xylorhiza tortifolia is a perennial herb or subshrub with branching, hairy, glandular stems that reach 60–80 centimetres (24–31 in) in height/length. The leaves are linear, lance-shaped, or oval, with pointed or spiny tips and spiny edges. The leaf surfaces are hairy and glandular.
The inflorescence is a solitary flower head borne on a long peduncle. The head has a base with long, narrow phyllaries which may be over 2 centimeters long. The head contains up to 60 or more lavender, pale blue, or white ray florets which may be over 3 centimeters long. The bloom period is March through June.
- Xylorhiza tortifolia var. imberbis — Imberis woodyaster, Great Basin region in Nevada, Utah, Arizona.
- Xylorhiza tortifolia var. parashantensis — Parashant woodyaster, endemic to Arizona.
- Xylorhiza tortifolia var. tortifolia — Mojave aster, Mojave woodyaster, a variety primarily native to the higher/winter colder Mojave Desert, and Owens Valley of the Great Basin region, from 240–2,000 metres (790–6,560 ft) in elevation.
Desert species of this aster with a woody base (Xylorhiza means woody base) are classified under the genus Xylorhiza, and have been removed from the large and complex genus Machaeranthera, where they were placed for many decades. A similar species, Xylorhiza wrightii−Big Bend aster, is native to the Chihuahuan Desert in western Texas and northern Mexico.
- Calflora: Xylorhiza tortifolia
- Flora of North America − Xylorhiza tortifolia
- USDA: Xylorhiza tortifolia var. imberbis
- USDA: Xylorhiza tortifolia var. parashantensis
- Calflora: Xylorhiza tortifolia var. tortifolia
- Jepson eFlora: Xylorhiza tortifolia var. tortifolia
- Lady Bird Johnson Wildflower Center Native Plant Information Network−NPIN: Xylorhiza cognata (Mojave aster, Mojave woodyaster)
- Native American Ethnobotany Database: Xylorhiza tortifolia var. tortifolia
- Calflora Database: Xylorhiza tortifolia (Mojave woodyaster)
- USDA Plants Profile for Xylorhiza tortifolia (Mojave woodyaster)
- Jepson Manual eFlora (TJM2) treatment of Xylorhiza tortifolia var. tortifolia
- UC Photos gallery for Xylorhiza tortifolia
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