Syn.: Amellus spinulosus Pursh, Aster pinnatifidus (Hook.) Kuntze, Aster spinuliger (A. Gray) Kuntze, Chrysopsis lamarckii (Cass.) Nutt., Dieteria spinulosa (Pursh) Nutt., Eriocarpum australe Greene, Eriocarpum spinulosum (Pursh) Greene, Haplopappus spinulosus (Pursh) DC., Machaeranthera australis (Greene) Shinners, Machaeranthera laevis (Wooton et Standl.) Shinners, Machaeranthera pinnata (Nutt.) Shinners, Machaeranthera pinnatifida var. pinnatifida (Hook.) Shinners, Machaeranthera pinnatifida subsp. pinnatifida (Hook.) Shinners, Sideranthus australe (Greene) Rydb., Sideranthus australis (Greene) Rydb., Sideranthus cotula Small, Sideranthus laevis Wooton et Standl., Sideranthus machaeranthera Small, Sideranthus puberulus Rydb., Sideranthus spinulosus (Pursh) Sweet ex Rydb., Starkea pinnata Nutt.
Family: Asteraceae Bercht. et J. Presl
Distribution: Central regions of North America, from Alberta, Saskatchewan, Manitoba, through Nebraska, Oklahoma and Texas to northern Mexico (Baja California, Chihuahua, Coahuila, Durango, Nuevo Leon, San Luis Potosi, Sonora, Tamaulipas, Zacatecas). Eastward it reaches Iowa, Minnesota and westward to Arizona and southeast California. Morphologically quite variable, 7 varieties are recognized.
Ecology: Grows in prairie, semi-deserts, sometimes in mountain valleys, where the isolated populations demonstrate the morphological variations. It occupies disturbed areas as well. Blooms in late summer.
Description: Perennial herb to subshrub, 10–100 cm tall. Stem erect to ascending, branched, woody base. Basal leaves sometimes withering by flowering, divided pinnately into 2+ deep lobes, 1.5–3 × 0.8–1.3 cm, margins smooth or dentate, each tipped with a white bristle, hairy or smooth or glandular. Bracts in 5–6 rows, linear or narrowly lanceolate, smooth or hairy; ray florets 14–60, yellow, 5–12 mm long; disc florets 30–150+, yellow, 4–5 mm. Fruit is an achene, narrowly obovoid, 1.8–2.5 mm, pappus tawny, 4.6 mm, with bristles.
Note: Genus Xanthisma includes 17 species spread over North America. It was separated from the numerous genus Machaeranthera.
These images were taken in Canada, Alberta, Calgary, Irrigation Canal (August 12, 2013).
