Taxon Report

Boechera johnstonii (Munz) Al-Shehbaz

Johnston's rockcress

Print Report


Taxon Summary

Boechera johnstonii, commonly known as Johnston's rockcress, is a perennial herb in the Brassicaceae that is found only in California. It occurs within Chaparral, and Lower montane coniferous forest, growing at elevations from 1350 to 2150 meters. Boechera johnstonii is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

  Classification
Scientific Name:
 Boechera johnstonii (Munz) Al-Shehbaz
Common Name:
 Johnston's rockcress
Family: Brassicaceae
Element Code: PDBRA060Y0
USDA Plants Symbol:
Synonyms/Other Names:
  • Arabis johnstonii Munz

Ecology and Life History
Lifeform: perennial herb
Blooming Period: Feb-Jun Feb-Jun
Elevation: 1350-2150 (4430-7055)
General Habitats: Chaparral, Lower montane coniferous forest
Microhabitat: Clay
Microhabitat Details: often on eroded clay

Conservation Status
CA Rare Plant Rank: 1B.2
Global Rank: G1
State Rank:
 S1
State List: None
Fed List: None
Other Status: SB_CalBG/RSABG; USFS_S
CRPR Changes:

Occurrence Data from the CNDDB
Total Occurrences: 10
Element Occurrence Ranks:
   Excellent (A) 1
   Good (B) 0
   Fair (C) 0
   Poor (D) 0
   None (X) 0
   Unknown (U) 9

Location
California Endemic:  True
California Counties and Islands: Name (Code)
Riverside (RIV)
Quads: Name (Quad Code)
Anza (3311656), Butterfly Peak (3311655), Idyllwild (3311666), Palm View Peak (3311665), San Jacinto Peak (3311676)

Threat List Data from the CNDDB

Threat List Total: 7
EOs with Threat Listed: Total EOs % of EOs
7 70 %
Grazing 7 70%
Foot traffic/trampling 6 60%
Development 5 50%
Non-native plant impacts 5 50%
Wood cutting or brush clearing 3 30%
Recreational use (non-ORV) 2 20%
Road/trail construction/maint. 2 20%

Notes
Known only from the southern San Jacinto Mtns. Threatened by recreational and residential development in Garner Valley. Also threatened by grazing and trampling, and possibly threatened by vegetation/fuels management projects. Boechera hirshbergiae is treated as a synonym of this plant in TJM 2; see Harvard Papers in Botany 11(1):61-88 (2006) for relative taxonomic treatment. See Bulletin of the Southern California Academy of Sciences 31:62-63 (1932) for original description, Rhodora 43(511):467-468 (1941) for taxonomic treatment, and Novon 13(4):381-391 (2003) for revised nomenclature.
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 25 October 2025].