Thelypodium stenopetalum
Slender-petaled thelypodium
(c) Trevor Van Loon, some rights reserved (CC BY) · licence
Family: Brassicaceae · Type: Herb · Native
Conservation status: CNPS 1B.1 · Endangered
Thelypodium stenopetalum (Slender-petaled thelypodium) is a native California herb in the Brassicaceae family, recognized by no sympatric congeners.
Slender-petaled thelypodium is a rare (CNPS 1B.1) California native biennial found in Big Bear Valley in alkaline flats and lake shores at elevations of 1,900 to 2,200 meters. Flowering from May to August, this plant produces lavender to white flowers 5 to 8 millimeters long with delicate crinkled petals. Growing 3 to 9 decimeters tall with simple or branched stems that are glaucous and mostly hairless, it develops an open inflorescence that expands significantly when fruiting. Its basal leaves are 1 to 4 centimeters long, entire and wavy, typically withering by fruiting time, while mid-stem leaves are sessile and sagittate, clasping the stem. The cylindric fruit develops 2.5 to 5 centimeters long, containing 50 to 82 plump seeds.
Identification and appearance
Key characters: Geographically isolated; no sympatric congeners
Habitat and range
Habitat: Alkaline flats, lake shores
Elevation: 1900-2200 m
California counties: San Bernardino, Mariposa
Bloom period
Thelypodium stenopetalum blooms May-Aug.
Conservation status
CNPS 1B.1 · Endangered
How to tell it apart
vs Stanleya: Flower stalks barely visible versus quarter-inch-plus dramatic stalks in Stanleya.; vs Caulanthus: Seed pods sit on distinct stalks above flower base versus sitting directly on base.; vs Brassica: Purple to white flowers with stalked pods versus yellow flowers in Brassica.; vs Boechera: Robust plants with relatively large flowers (6-16mm) versus delicate plants with smaller flowers.; vs Noccaea: Tall stems with purple-white flowers versus low rosette plants with tiny white flowers.
Frequently asked questions
Is Thelypodium stenopetalum native to California?
Yes. Thelypodium stenopetalum is native to California (recorded as native).
When does Thelypodium stenopetalum bloom?
Thelypodium stenopetalum blooms May-Aug.
Where in California does Thelypodium stenopetalum grow?
Thelypodium stenopetalum occurs in San Bernardino, Mariposa, at elevations of 1900-2200 m.
What plant family does Thelypodium stenopetalum belong to?
Thelypodium stenopetalum is in the Brassicaceae family, genus Thelypodium.
Is Thelypodium stenopetalum rare or endangered?
Thelypodium stenopetalum carries California Rare Plant Rank 1B.1, state rank S1.
Related species
Other California species in the same genus, family, or bioregion.
- Thelypodium brachycarpum — Short-podded thelypodium
- Thelypodium crispum — Crisped thelypody
- Thelypodium flexuosum — Nodding thelypodium
- Thelypodium howellii subsp. howellii — Howell's thelypodium
- Thelypodium integrifolium — Entire leaved thelypodium
- Thelypodium integrifolium subsp. affine
- Thlaspi arvense — Fan weed
- Thlaspi sp. — Pennycress
- Thysanocarpus conchuliferus — Santa cruz island fringepod
- Thysanocarpus curvipes — Fringe pod
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.