Arnica discoidea
Rayless arnica
(c) Ken-ichi Ueda, some rights reserved (CC BY), uploaded by Ken-ichi Ueda · licence
Family: Asteraceae · Type: Herb · Native
Arnica discoidea (Rayless arnica) is a native California herb in the Asteraceae family, recognized by complete absence of ray flowers is unique.
Rayless arnica is a California native perennial found in northwestern California, the Cascade Range, northern and central Sierra Nevada, southern Sierra Nevada, central western California, western Transverse Ranges, San Bernardino Mountains, western Peninsular Ranges, and Modoc Plateau in chaparral and foothill woodland at elevations of 100 to 1,500 meters. Flowering from May to July, this plant produces yellow disk flowers in discoid heads without ray flowers, creating a distinctive buttonlike appearance. Growing 15 to 60 centimeters tall with generally a single stem that may be branched, it has long and short-glandular hairs covering its structure. Its basal leaves form prominent sterile rosettes, with 3 to 7 pairs of cauline leaves that are lanceolate to ovate, 2 to 12 centimeters long and slightly toothed, becoming smaller toward the stem's tip. The fruit is 6 to 8 millimeters long, covered with forked hairs and stalked glands, topped with a short white plumose pappus.
Identification and appearance
Key characters: 16 sympatric species; complete absence of ray flowers is unique
Habitat and range
Habitat: Chaparral, foothill woodland
Elevation: 100-1500 m
Outside California: to Washington, western Nevada
Bloom period
Arnica discoidea 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 discoidea native to California?
Yes. Arnica discoidea is native to California (recorded as native).
When does Arnica discoidea bloom?
Arnica discoidea blooms May-Jul.
What plant family does Arnica discoidea belong to?
Arnica discoidea is in the Asteraceae family, genus Arnica.
What habitat does Arnica discoidea grow in?
Arnica discoidea grows in Chaparral, foothill woodland.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · 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.