Rhinotropis subspinosa
Spiny milkwort, Spiny Milkwort
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Family: Polygalaceae · Type: Shrub · Native
Conservation status: CNPS 2B.2
Rhinotropis subspinosa (Spiny milkwort) is a native California shrub in the Polygalaceae family, recognized by . Key features: larger flowers with prominent yellow keel beak vs tiny flowers without beak.
Spiny milkwort is a rare (CNPS 2B.2) California native perennial found in the Lassen County and Sweetwater Mountains in desert scrub and volcanic mesa habitats at elevations of 1,350 to 2,285 meters. Flowering from June to July, this plant produces small pink and yellow flowers with distinctive wing-like sepals and a yellow or greenish keel petal beak. Growing with compact stems less than 25 centimeters tall, it has a delicate shrub-like structure with stems that are glabrous or occasionally covered in short stiff hairs. Its leaves are small, measuring 4 to 31 millimeters long, with obovate or elliptic shapes and acuminate bases, generally appearing smooth or with occasional short stiff hairs. The plant produces fruits 5.5 to 10 millimeters long, with seeds that are evenly hairy and elliptically shaped.
Identification and appearance
Key characters: 2 sympatric species. Key features: larger flowers with prominent yellow keel beak vs tiny flowers without beak
Habitat and range
Habitat: Desert scrub, volcanic mesas
Elevation: 1350-2285 m
California counties: Lassen, Mono, Inyo
Outside California: to Utah, southwestern Colorado, northwestern New Mexico, northern Arizona
Bloom period
Rhinotropis subspinosa blooms Jun-Jul.
Conservation status
CNPS 2B.2
Frequently asked questions
Is Rhinotropis subspinosa native to California?
Yes. Rhinotropis subspinosa is native to California (recorded as native).
When does Rhinotropis subspinosa bloom?
Rhinotropis subspinosa blooms Jun-Jul.
Where in California does Rhinotropis subspinosa grow?
Rhinotropis subspinosa occurs in Lassen, Mono, Inyo, at elevations of 1350-2285 m.
What plant family does Rhinotropis subspinosa belong to?
Rhinotropis subspinosa is in the Polygalaceae family, genus Rhinotropis.
Is Rhinotropis subspinosa rare or endangered?
Rhinotropis subspinosa carries California Rare Plant Rank 2B.2, state rank S3.
Related species
Other California species in the same genus, family, or bioregion.
- Rhinotropis acanthoclada — Thorny milkwort
- Rhinotropis californica — California milkwort
- Rhinotropis cornuta — Sierra milkwort
- Rhinotropis cornuta var. cornuta — Sierra milkwort
- Rhinotropis cornuta var. fishiae — Fish's milkwort
- Rhinotropis heterorhyncha — Notch-beaked milkwort
- Polygala myrtifolia — myrtle-leaf milkwort
- Polygalaceae sp. — Milkwort family
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.