Arabis pycnocarpa var. pycnocarpa
Hairy fruit rock cress
Mason Brock ( Masebrock ) (via Wikimedia Commons) · CC0
Family: Brassicaceae · Type: Herb · Native
Arabis pycnocarpa var. pycnocarpa (Hairy fruit rock cress) is a native California herb in the Brassicaceae family, recognized by white flowers and numerous sagittate-based cauline leaves.
Hairy fruit rock cress is a California native perennial found in the Klamath Ranges, northern Coast Ranges, Cascade Range, Sierra Nevada, San Bernardino Mountains, and White and Inyo Mountains in gravelly soils, meadows, and shady slopes at elevations below 2,500 meters. Flowering from March to July, this plant produces delicate white flowers 3.5 to 5 millimeters long with narrow petals. Growing with multiple erect stems 10 to 80 centimeters tall that can be simple or branched, it develops a variable branched or unbranched caudex. Its leaves range from basal oblong or spoon-shaped rosettes to cauline leaves that are ovate to lanceolate, often with arrow-shaped or lobed bases. The elongated fruits measure 4 to 6 centimeters long, giving the plant its distinctive "hairy fruit" common name.
Identification and appearance
Key characters: 4 sympatric species; key features are white flowers and numerous sagittate-based cauline leaves
Habitat and range
Habitat: Gravelly soils, swales, disturbed sites, meadows, shady slopes, occasionally moist
Elevation: < 2500 m
California counties: San Bernardino, Mono, Trinity, Tehama, Modoc, Inyo, Fresno, Marin, Siskiyou, Shasta, Del Norte, El Dorado
Outside California: Canada, United States except Alaska, Hawaii
Bloom period
Arabis pycnocarpa var. pycnocarpa blooms Mar-Jul.
How to tell it apart
vs Boechera: Arabis pods are narrower (under 2mm vs 2mm+) and consistently straight; Boechera pods are often curved.; vs Matthiola: Arabis has stalked star-shaped hairs and erect narrow pods; Matthiola has soft unbranched hairs and stouter pods.; vs Raphanus: Arabis has tiny star-shaped hairs and thin erect pods; Raphanus has larger flowers and thick beaded pods.; vs Pelargonium: Arabis has four petals and narrow upright pods; Pelargonium has five petals and beak-like fruits.; vs Phlox: Arabis has four separate petals and seed pods; Phlox has fused tubular flowers and capsules.
Frequently asked questions
Is Arabis pycnocarpa var. pycnocarpa native to California?
Yes. Arabis pycnocarpa var. pycnocarpa is native to California (recorded as native).
When does Arabis pycnocarpa var. pycnocarpa bloom?
Arabis pycnocarpa var. pycnocarpa blooms Mar-Jul.
Where in California does Arabis pycnocarpa var. pycnocarpa grow?
Arabis pycnocarpa var. pycnocarpa occurs in San Bernardino, Mono, Trinity, Tehama, Modoc, Inyo, Fresno, Marin and other counties, at elevations of < 2500 m.
What plant family does Arabis pycnocarpa var. pycnocarpa belong to?
Arabis pycnocarpa var. pycnocarpa is in the Brassicaceae family, genus Arabis.
What habitat does Arabis pycnocarpa var. pycnocarpa grow in?
Arabis pycnocarpa var. pycnocarpa grows in Gravelly soils, swales, disturbed sites, meadows, shady slopes, occasionally moist.
Related species
Other California species in the same genus, family, or bioregion.
- Arabis rigidissima var. demota — Galena Creek rockcress
- Arabis rigidissima var. rigidissima — Trinity Mountains rockcress
- Arabis sp. — Rockcress
- Arabis aculeolata — Waldo rockcress
- Arabis blepharophylla — Coast rockcress
- Arabis eschscholtziana — Eschscholtz's hairy rockcress
- Armoracia rusticana — Horse radish
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.