Brewer’s Rockcress

Until recently, Brewer’s rockcress (Boechera brewerii) was a member of the Arabis genus. DNA analysis demonstrated chromosomal differences that led to it being reassigned to the genus Boechera. Thus Brewer’s rockcress is seen in the literature as both Arabis brewerii and Boechera brewerii. The species name, brewerii, honors William Henry Brewer (1828 – 1910), and American botanist and professor who explored the flora of California and the Pacific Northwest. The Danish botanist, Tyge W. Bocher (1909 – 1983), gives his name to the genus designation, Boechera. Bocher’s specialty was alpine plants.

Brewer’s rockcress, a member of the Mustard Family, is a native perennial found below 7,400 feet in California and Oregon. Its habitat is rocky areas in woodlands.

The Brewer’s rockcress stem rises from a woody, branching rootstock. The basal leaves  are oval to lanceolate while the cauline (stem) leaves are auriculate (have no stalk and clasp the stem). The stems and leaves of Brewer’s rockcress are hairy.

Seven to 20 flowers arranged in a raceme (unbranched and maturing from the bottom up) form the inflorescence. Dark purple, hairy sepals surround the four lighter purple or lavender petals.

The fruit is a long, narrow silique – maturing to purple. The silique (seed capsule formed by 2  fused carpels that is more than three times longer than wide) is usually curved and contains a single row of narrowly winged seeds.

Leonard and I found these Brewer’s rockcress specimens along the McCloud River arm of Lake Shasta (Gilliam Road, Shasta County CA) in late February – one of the first wildflowers in bloom this year.

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