Arabis mcdonaldiana
Mcdonald's rockcress, McDonald's rockcress, McDonald's rockcress
(c) Trevor Van Loon, some rights reserved (CC BY) · licence
Family: Brassicaceae · Type: Herb · Native
Conservation status: CNPS 1B.1 · Endangered
Arabis mcdonaldiana (Mcdonald's rockcress) is a native California herb in the Brassicaceae family, recognized by purple flowers, glabrous habit, and non-lobed cauline leaves.
McDonald's rockcress is a rare (CNPS 1B.1) California native perennial found in the northern Coast Ranges on deep red soils, steep slopes, dry ridges, and serpentine areas at elevations of 200 to 1,800 meters. Flowering from May to June, this plant produces purple flowers with spoon-shaped petals 8 to 16 millimeters long. Growing with slender stems 15 to 40 centimeters tall, it develops a branched caudex with few to many simple stems. Its basal leaves are 1 to 4 centimeters long, entire to wavy-margined, with cauline leaves spaced along the stem, oblong and unlobed. The fruit is an erect to ascending silique 2 to 4 centimeters long and 1.5 to 2 millimeters wide.
Identification and appearance
Key characters: 3 sympatric species; key features are purple flowers, glabrous habit, and non-lobed cauline leaves
Habitat and range
Habitat: Deep +- red soils, steep slopes, dry ridges, serpentine areas
Elevation: 200-1800 m
Bloom period
Arabis mcdonaldiana blooms May-Jun.
Conservation status
CNPS 1B.1 · Endangered
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 mcdonaldiana native to California?
Yes. Arabis mcdonaldiana is native to California (recorded as native).
When does Arabis mcdonaldiana bloom?
Arabis mcdonaldiana blooms May-Jun.
What plant family does Arabis mcdonaldiana belong to?
Arabis mcdonaldiana is in the Brassicaceae family, genus Arabis.
Is Arabis mcdonaldiana rare or endangered?
Arabis mcdonaldiana carries California Rare Plant Rank 1B.1, state rank S3.
What habitat does Arabis mcdonaldiana grow in?
Arabis mcdonaldiana grows in Deep +- red soils, steep slopes, dry ridges, serpentine areas.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.