Tetradymia spinosa
Shortspine horsebrush
(c) Matt Lavin, some rights reserved (CC BY-SA) · licence
Family: Asteraceae · Type: Shrub · Native
Tetradymia spinosa (Shortspine horsebrush) is a native California shrub in the Asteraceae family, recognized by recurved spines and axillary head placement.
Shortspine horsebrush is a native shrub found in southern Modoc Plateau and northern Sierra Nevada Eastern Slopes in saltbush scrub at elevations of 800 to 2,400 meters. Flowering from April to June, this plant produces yellow flowers in small clusters with heads 8 to 12 millimeters long. Growing as a compact shrub up to 1 meter tall with distinctively spiny branches, it develops rigid, recurved spines that form part of its structural character. Its leaves are notable for their varied form, with main leaves 5 to 25 millimeters long forming sharp spines and clustered leaves that are thread-like to nearly oblanceolate. The plant's fruits are densely covered in long white hairs, adding to its distinctive appearance in arid landscapes.
Identification and appearance
Key characters: 6 sympatric species; diagnostic recurved spines and axillary head placement
Habitat and range
Habitat: Generally saltbush scrub
Elevation: 800-2400 m
Outside California: to Oregon, Montana, Wyoming, northern New Mexico
Bloom period
Tetradymia spinosa blooms Apr-Jun.
How to tell it apart
vs Ericameria: Tetradymia has 4-6 bracts in 1-2 rows; Ericameria has many bracts in 5 vertical rows.; vs Artemisia: Tetradymia has rigid spine-tipped branches; Artemisia has soft, non-spiny aromatic foliage.; vs Lycium: Tetradymia has yellow composite flowers; Lycium has tubular purple/greenish flowers with 5 petals.; vs Senecio: Tetradymia has 4-8 flowers per head with woolly appearance; Senecio has more flowers per head and often ray petals.; vs Krascheninnikovia: Tetradymia has yellow composite flowers; Krascheninnikovia has tiny greenish flowers without petals (Chenopodiaceae family).
Frequently asked questions
Is Tetradymia spinosa native to California?
Yes. Tetradymia spinosa is native to California (recorded as native).
When does Tetradymia spinosa bloom?
Tetradymia spinosa blooms Apr-Jun.
What plant family does Tetradymia spinosa belong to?
Tetradymia spinosa is in the Asteraceae family, genus Tetradymia.
What habitat does Tetradymia spinosa grow in?
Tetradymia spinosa grows in Generally saltbush scrub.
Related species
Other California species in the same genus, family, or bioregion.
- Tetradymia stenolepis — Mojave cottonthorn
- Tetradymia tetrameres — Dune horsebrush
- Tetradymia argyraea — Striped horsebrush
- Tetradymia axillaris — Catclaw horsebrush
- Tetradymia axillaris var. axillaris — Catclaw horsebrush
- Tetradymia axillaris var. longispina — Catclaw horsebrush
- Tetraneuris acaulis var. arizonica — Arizona four nerve daisy
- Tetraneuris sp.
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.