Taxon Report

Arabis mcdonaldiana Eastw.

McDonald's rockcress

Print Report

Taxon Summary

Arabis mcdonaldiana, commonly known as McDonald's rockcress, is a perennial herb in the Brassicaceae that is found in California and elsewhere. It occurs within Lower montane coniferous forest, and Upper montane coniferous forest, growing at elevations from 135 to 1800 meters. Arabis mcdonaldiana is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

Classification


Scientific Name:	Arabis mcdonaldiana Eastw.
Common Name:	McDonald's rockcress
Family:	Brassicaceae
Element Code:	PDBRA06150
USDA Plants Symbol:
Synonyms/Other Names:	Arabis macdonaldiana East.

Ecology and Life History


Lifeform:	perennial herb
Blooming Period: May-Jul	May-Jul
Elevation:	135-1800 (445-5905)
General Habitats:	Lower montane coniferous forest, Upper montane coniferous forest
Microhabitat:	Serpentine
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.1
Global Rank:	G3
State Rank:	S3
State List:	CE
Fed List:	FE
Other Status:	SB_BerrySB; SB_CalBG/RSABG
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	29
Element Occurrence Ranks:
Excellent (A)	8
Good (B)	7
Fair (C)	1
Poor (D)	0
None (X)	0
Unknown (U)	13

Location


California Endemic: False
California Counties and Islands: Name (Code)
Del Norte (DNT), Mendocino (MEN), Siskiyou (SIS)
Quads: Name (Quad Code)
Broken Rib Mtn. (4112386), Devils Punchbowl (4112376), Gasquet (4112378), High Divide (4112481), High Plateau Mtn. (4112388), Noble Butte (3912386), Polar Bear Mtn. (4112385), Preston Peak (4112375), Shelly Creek Ridge (4112387)

Threat List Data from the CNDDB


Threat List Total:	4
EOs with Threat Listed:	Total EOs	% of EOs
	13	45 %
Mining	10	34%
Road/trail construction/maint.	3	10%
Grazing	1	3%
Other	1	3%

Notes



Potentially threatened by mining. Endangered in OR, where plant needs taxonomic study. Includes A. serpentinicola. See Rhodora 43(511):350 (1941) for taxonomic treatment, and Contributions from the Gray Herbarium 204:149-154 (1973) for taxonomic information.
Threats:

Taxonomy:

Selected References

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 31 January 2025].