Oxypolis occidentalis
Western cow bane
(c) Katherine Baird, some rights reserved (CC BY) · licence
Family: Apiaceae · Type: Herb · Native
Oxypolis occidentalis (Western cow bane) is a native California herb in the Apiaceae family, recognized by Western range edge of primarily eastern North American genus.
Western cow bane is a California native perennial found in the Sierra Nevada, northern California ranges, and White and Inyo Mountains in bogs, wet meadows, and stream sides within conifer forests at elevations below 2,700 meters. Flowering from July to August, this plant produces small white flowers in compound umbels with 12 to 24 rays extending 2 to 8.5 centimeters. Growing 60 to 150 centimeters tall with erect, slender stems, it develops a robust herbaceous structure with enlarged leaf petioles. Its distinctive leaves are one-pinnate with 5 to 13 leaflets, each 3.5 to 9.5 centimeters long, ranging from lanceolate to widely ovate with crenate or serrate edges. The fruit is an oblong or ovate structure measuring 5 to 6 millimeters in length.
Identification and appearance
Key characters: Western range edge of primarily eastern North American genus
Habitat and range
Habitat: Bogs, wet meadows, stream sides, generally in conifer forest
Elevation: < 2700 m
California counties: Fresno, Tulare, San Bernardino, El Dorado, Madera, Los Angeles, Tuolumne, Butte, Tehama, Plumas, Humboldt, Lassen, Sierra, Mariposa, Calaveras, Inyo, Kern, Siskiyou
Outside California: Oregon, British Columbia
Bloom period
Oxypolis occidentalis blooms Jul-Aug.
How to tell it apart
vs Oenanthe: Oxypolis fruits are flat with thin wings; Oenanthe fruits are rounded and corky with a crown.; vs Sium: Oxypolis fruits are flattened front-to-back; Sium fruits are rounded with thick corky ribs.; vs Berula: Oxypolis fruits are flat with broad wings; Berula fruits are rounded with hidden ribs.; vs Apium: Oxypolis fruits are flattened with wings; Apium fruits are rounded without wings.; vs Perideridia: Oxypolis grows in mountain bogs; Perideridia grows in dry grasslands with seasonal dormancy.
Frequently asked questions
Is Oxypolis occidentalis native to California?
Yes. Oxypolis occidentalis is native to California (recorded as native).
When does Oxypolis occidentalis bloom?
Oxypolis occidentalis blooms Jul-Aug.
Where in California does Oxypolis occidentalis grow?
Oxypolis occidentalis occurs in Fresno, Tulare, San Bernardino, El Dorado, Madera, Los Angeles, Tuolumne, Butte and other counties, at elevations of < 2700 m.
What plant family does Oxypolis occidentalis belong to?
Oxypolis occidentalis is in the Apiaceae family, genus Oxypolis.
What habitat does Oxypolis occidentalis grow in?
Oxypolis occidentalis grows in Bogs, wet meadows, stream sides, generally in conifer forest.
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.