Arnica sororia
Twin arnica, Twin Arnica
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Family: Asteraceae · Type: Herb · Native
Arnica sororia (Twin arnica) is a native California herb in the Asteraceae family, recognized by sagebrush habitat and yellow-orange rays are key.
Twin arnica is a California native perennial found in the Great Basin in open sagebrush scrub at elevations of 1,400 to 1,800 meters. Flowering from May to July, this plant produces yellow-orange ray flowers in radiate heads 10 to 15 millimeters wide. Growing with stems 10 to 50 centimeters tall, emerging from a short, sparsely scaly rhizome, the plant can be single or branched with stalked-glandular and uneven hairiness. Its basal leaves are densely clustered, with oblanceolate blades 3.5 to 14.5 centimeters long, while cauline leaves are 3 to 6 pairs and crowded toward the base. The fruit is 3 to 5.5 millimeters long, covered in hairs and topped with a short-barbed white pappus.
Identification and appearance
Key characters: 7 sympatric species; sagebrush habitat and yellow-orange rays are key
Habitat and range
Habitat: Uncommon. Open sagebrush scrub
Elevation: 1400-1800 m
Outside California: to western Canada, Wyoming
Bloom period
Arnica sororia blooms May-Jul.
How to tell it apart
vs Senecio: Senecio has alternate leaves; Arnica leaves opposite in pairs - check leaf arrangement first; vs Wyethia: Wyethia has large basal leaves and many-ranked bracts; Arnica stem leaves opposite, bracts in 2 series; vs Packera: Packera has alternate leaves; Arnica leaves opposite in pairs up stem; vs Kyhosia: Kyhosia has alternate leaves; Arnica leaves opposite - check where leaves attach to stem; vs Helianthella: Helianthella leaves mostly alternate; Arnica leaves strictly opposite in pairs
Frequently asked questions
Is Arnica sororia native to California?
Yes. Arnica sororia is native to California (recorded as native).
When does Arnica sororia bloom?
Arnica sororia blooms May-Jul.
What plant family does Arnica sororia belong to?
Arnica sororia is in the Asteraceae family, genus Arnica.
What habitat does Arnica sororia grow in?
Arnica sororia grows in Uncommon. Open sagebrush scrub.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.