Symphyotrichum occidentale
Western mountain aster
Family: Asteraceae (Compositae) · Type: Herb · Native
Symphyotrichum occidentale (Western mountain aster) is a native California herb in the Asteraceae (Compositae) family.
Western mountain aster is a California native perennial found in mountain and subalpine regions with rocky or open habitats at elevations ranging from high-elevation mountain zones. Flowering from July to September, this plant produces delicate violet ray flowers 8 to 12 millimeters long in open, cluster-like arrangements. Growing with erect stems 15 to 45 centimeters tall, it develops from a long rhizomatous root system and can be glabrous or slightly hairy. Its leaves range from 5 to 15 centimeters long, becoming progressively smaller toward the stem's tip, with acute edges and a nearly entire margin. The plant's distinctive flower heads feature linear to oblong phyllaries with green tips and pale margins, creating an elegant mountain wildflower profile.
Identification and appearance
Key characters: Geographically isolated from all congeners
Habitat and range
California counties: Lassen, Mono, San Bernardino, Placer, Tulare, Tuolumne, Fresno, Amador, Trinity, Mariposa, Alpine, Siskiyou, Calaveras, Nevada, Plumas, Riverside, Inyo, Shasta, Sierra, El Dorado, Butte, Madera, Kern, Lake, Yuba, Colusa, Mendocino, Stanislaus, Humboldt, Napa, Del Norte, Sutter, Solano, Modoc, Tehama, Sacramento, Sonoma, Santa Clara, San Joaquin, Ventura, San Luis Obispo, Alameda, Yolo
How to tell it apart
vs Corethrogyne: Corethrogyne has distinctive brown/reddish pappus; Symphyotrichum has white pappus; vs Erigeron: Erigeron has 50+ very thin rays per head; Symphyotrichum has fewer wider rays; vs Eurybia: Eurybia has two-toned bracts (green tips, white bases); Symphyotrichum bracts are all green; vs Aster: Aster is the old name for Symphyotrichum - they're the same plants; vs Dieteria: Dieteria has spinulose-tipped bracts; Symphyotrichum bracts lack spiny tips
Frequently asked questions
Is Symphyotrichum occidentale native to California?
Yes. Symphyotrichum occidentale is native to California (recorded as native).
Where in California does Symphyotrichum occidentale grow?
Symphyotrichum occidentale occurs in Lassen, Mono, San Bernardino, Placer, Tulare, Tuolumne, Fresno, Amador and other counties.
What plant family does Symphyotrichum occidentale belong to?
Symphyotrichum occidentale is in the Asteraceae (Compositae) family, genus Symphyotrichum.
Related species
Other California species in the same genus, family, or bioregion.
- Symphyotrichum occidentale var. intermedius — Larger western mountain aster
- Symphyotrichum occidentale var. occidentale
- Symphyotrichum occidentale var. yosemitanum — Western bog aster
- Symphyotrichum sp. — American-aster
- Symphyotrichum spathulatum var. spathulatum — Western mountain aster
- Symphyotrichum subspicatum — Douglas aster
- Verbesina encelioides
- Verbesina encelioides subsp. exauriculata — Golden crownbeard
- Xylorhiza tortifolia — Mojave-aster
Sources: Index of California Plant Names · CalPhotos
Last updated 2026-10-08
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.