Perideridia howellii
Howell's yampah
Family: Apiaceae · Type: Herb · Native
Perideridia howellii (Howell's yampah) is a native California herb in the Apiaceae family, recognized by fibrous roots and corky fruit ribs diagnostic.
Howell's yampah is a California native perennial found in the Klamath Ranges, northern Coast Ranges, Cascade Range, northern Sierra Nevada, and central Sierra Nevada Forest in moist meadows, ravines, and streambanks at elevations of 100 to 1,500 meters. Flowering from July to August, this plant produces white flowers in delicate umbels with 17 to 20 spreading rays. Growing 80 to 160 centimeters tall with fibrous roots clustered in groups of more than 15, it develops substantial lanceolate basal leaves up to 50 centimeters long that are intricately 2-pinnate. Its leaves feature deeply toothed leaflets 2 to 7 centimeters long, with distinctive linear-spoon-shaped bracts that have scarious margins and are reflexed. The fruit is an oblong structure 4 to 6 millimeters long with conspicuously corky ribs and a single oil tube between each rib.
Identification and appearance
Key characters: 13 sympatric species; fibrous roots and corky fruit ribs diagnostic
Habitat and range
Habitat: Moist meadows, ravines, streambanks
Elevation: 100-1500 m
California counties: Siskiyou, Sierra, Plumas, Sonoma, Butte, Colusa, Tehama, Mendocino, Humboldt, Lake, Nevada, Del Norte, Mariposa, Calaveras, Shasta
Outside California: Oregon
Bloom period
Perideridia howellii blooms Jul-Aug.
How to tell it apart
vs Ligusticum: Perideridia grows from tubers in grasslands; Ligusticum grows from taproots in mountain forests.; vs Daucus: Perideridia fruits are rounded with thin ribs; Daucus fruits are bristly and form a bird's-nest cluster.; vs Eriogonum: Eriogonum is in the buckwheat family with papery flowers; Perideridia has carrot-family umbels.; vs Angelica: Perideridia has small rounded fruits; Angelica has large flattened fruits with broad wings.; vs Achillea: Achillea is in the sunflower family with flat-topped flower heads; Perideridia has carrot-family umbels.
Frequently asked questions
Is Perideridia howellii native to California?
Yes. Perideridia howellii is native to California (recorded as native).
When does Perideridia howellii bloom?
Perideridia howellii blooms Jul-Aug.
Where in California does Perideridia howellii grow?
Perideridia howellii occurs in Siskiyou, Sierra, Plumas, Sonoma, Butte, Colusa, Tehama, Mendocino and other counties, at elevations of 100-1500 m.
What plant family does Perideridia howellii belong to?
Perideridia howellii is in the Apiaceae family, genus Perideridia.
What habitat does Perideridia howellii grow in?
Perideridia howellii grows in Moist meadows, ravines, streambanks.
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.