Osmadenia tenella
Osmadenia, Osmadenia
Photo by Chez Brungraber
Family: Asteraceae · Type: Herb · Native
Osmadenia tenella (Osmadenia) is a native California herb in the Asteraceae family, recognized by Endemic monotypic genus with distinctive floral morphology.
Osmadenia is a California native annual herb found in southwestern California (excluding the Channel Islands) in coastal sage scrub, grassland, and oak savanna at elevations of 30 to 1,200 meters. Flowering from May to July, this plant produces white flowers that age to reddish tones, with ray flowers deeply three-lobed and occasionally displaying red splotches. Growing 20 to 40 centimeters tall with multiple thread-like spreading branches, it features strongly scented stems that are densely glandular and slightly rough. Its leaves are primarily linear and cauline, alternately arranged, with basal leaves 2 to 5 centimeters long that are scabrous and glandular with shaggy margins. The plant produces numerous small heads arranged in loose, cyme-like clusters with distinctive white ray flowers that transition to reddish hues as they mature.
Identification and appearance
Key characters: Endemic monotypic genus with distinctive floral morphology
Habitat and range
Habitat: Locally common. Barren, often rocky, sandy soils, coastal-sage scrub, grassland, oak savanna
Elevation: 30-1200 m
Outside California: Baja California
Bloom period
Osmadenia tenella blooms May-Jul.
How to tell it apart
vs Calycadenia: Osmadenia completely lacks sticky glands; Calycadenia covered with sticky tack glands.; vs Stephanomeria: Osmadenia has ray flowers; Stephanomeria has only tubular disc-like flowers, no rays.; vs Blepharizonia: Osmadenia lacks sticky glands; Blepharizonia sticky-glandular throughout.; vs Hemizonia: Osmadenia rays deeply fringed; Hemizonia rays shallowly lobed or entire.; vs Holocarpha: Osmadenia lacks sticky glands and pit glands; Holocarpha has pit-gland-tipped bracts.
Frequently asked questions
Is Osmadenia tenella native to California?
Yes. Osmadenia tenella is native to California (recorded as native).
When does Osmadenia tenella bloom?
Osmadenia tenella blooms May-Jul.
What plant family does Osmadenia tenella belong to?
Osmadenia tenella is in the Asteraceae family, genus Osmadenia.
What habitat does Osmadenia tenella grow in?
Osmadenia tenella grows in Locally common. Barren, often rocky, sandy soils, coastal-sage scrub, grassland, oak savanna.
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.