Idahoa scapigera
Oldstem idahoa
(c) Matt Berger, some rights reserved (CC BY), uploaded by Matt Berger · licence
Family: Brassicaceae · Type: Herb · Native
Idahoa scapigera (Oldstem idahoa) is a native California herb in the Brassicaceae family, recognized by Monotypic genus endemic to western North America; primitive position in Brassicaceae.
Oldstem idahoa is a California native annual found in northern California regions including Mount Saint Helena, the Cascade Range, northern Sierra Nevada, southern Sierra Nevada foothills, Mount Hamilton, and Great Basin areas in moist ledges, slopes, and meadows at elevations of 200 to 1,700 meters. Flowering from March to May, this delicate plant produces small white flowers on slender peduncles 2 to 13 centimeters long. Growing as a scapose plant with multiple thin stems, it forms a low basal rosette of leaves. Its leaves are distinctive, ranging from 7 to 20 millimeters long, with an ovate to spoon-shaped form, creating a compact ground-hugging growth pattern. The plant produces small round to wide-ovate silicles 6 to 9 millimeters long, each containing 6 to 10 seeds.
Identification and appearance
Key characters: Monotypic genus endemic to western North America; primitive position in Brassicaceae
Habitat and range
Habitat: Moist ledges, slopes, meadows, foothills
Elevation: 200-1700 m
California counties: Kern, Santa Clara, Trinity, Siskiyou, Modoc, Butte, Lassen, Plumas, Shasta, Tehama, Sierra, Lake, Calaveras, Napa, Alpine
Outside California: to British Columbia, Montana
Bloom period
Idahoa scapigera blooms Mar-May.
How to tell it apart
vs Cardamine: Idahoa's first flowers emerge singly from the basal rosette center, Cardamine has flowers arranged along stems.; vs Subularia: Idahoa grows on dry land in mountain meadows, Subularia is an aquatic plant growing in water.; vs Diplotaxis: Idahoa has flowers emerging singly from a ground rosette, Diplotaxis has yellow flowers in racemes on stems.; vs Lunaria: Idahoa is a tiny plant with single flowers from a basal rosette, Lunaria is tall with large papery pods.; vs Lepidium: Idahoa has flowers emerging singly directly from the ground-level rosette, Lepidium has branching flowering stems.
Frequently asked questions
Is Idahoa scapigera native to California?
Yes. Idahoa scapigera is native to California (recorded as native).
When does Idahoa scapigera bloom?
Idahoa scapigera blooms Mar-May.
Where in California does Idahoa scapigera grow?
Idahoa scapigera occurs in Kern, Santa Clara, Trinity, Siskiyou, Modoc, Butte, Lassen, Plumas and other counties, at elevations of 200-1700 m.
What plant family does Idahoa scapigera belong to?
Idahoa scapigera is in the Brassicaceae family, genus Idahoa.
What habitat does Idahoa scapigera grow in?
Idahoa scapigera grows in Moist ledges, slopes, meadows, foothills.
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.