Sidotheca emarginata
White-margined oxytheca
(c) Matt Berger, some rights reserved (CC BY), uploaded by Matt Berger · licence
Family: Polygonaceae · Type: Herb · Native
Conservation status: CNPS 1B.3
Sidotheca emarginata (White-margined oxytheca) is a native California herb in the Polygonaceae family, recognized by white flower cluster margins and fringed petals.
White-margined oxytheca is a rare (CNPS 1B.3) California native annual found in the eastern Peninsular Ranges, specifically in the Santa Rosa Mountains of Riverside County, growing in gravelly habitats at elevations of 1,200 to 2,500 meters. Flowering from February to August, this plant produces delicate white to pink flowers with fringed linear lobes, clustered in small groups of 3 to 6 blooms. Growing with compact stems 10 to 30 centimeters tall and spreading up to 5 centimeters wide, it forms low, intricate clusters. Its leaves are narrow and elongated, with blades 1.5 to 7.5 centimeters long and 0.4 to 1.5 centimeters wide, creating a delicate green backdrop for its distinctive white-margined involucre. The fruit is small, measuring 1.8 to 2 millimeters long, with white-edged bracts bearing subtle red-tinged awns.
Identification and appearance
Key characters: 2 sympatric species; distinguished by white flower cluster margins and fringed petals
Habitat and range
Habitat: Gravel
Elevation: 1200-2500 m
California counties: Riverside
Bloom period
Sidotheca emarginata blooms Feb-Aug.
Conservation status
CNPS 1B.3
How to tell it apart
vs Chorizanthe: Sidotheca has 5-6 awns per involucre and fringed petals; Chorizanthe typically has different awn counts and patterns.; vs Oxytheca: Sidotheca has fringed or 3-lobed petals; Oxytheca has smooth-edged, entire petals.; vs Acanthoscyphus: Sidotheca has 5-6 awns and fringed petals; Acanthoscyphus has 7-30+ awns and entire petals.
Frequently asked questions
Is Sidotheca emarginata native to California?
Yes. Sidotheca emarginata is native to California (recorded as native).
When does Sidotheca emarginata bloom?
Sidotheca emarginata blooms Feb-Aug.
Where in California does Sidotheca emarginata grow?
Sidotheca emarginata occurs in Riverside, at elevations of 1200-2500 m.
What plant family does Sidotheca emarginata belong to?
Sidotheca emarginata is in the Polygonaceae family, genus Sidotheca.
Is Sidotheca emarginata rare or endangered?
Sidotheca emarginata carries California Rare Plant Rank 1B.3, state rank S3.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CNPS Rare Plant Inventory · Index of California Plant Names · CalPhotos · CDFW CNDDB
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.