Taxon Report

Chorizanthe aphanantha K.M. Nelson & D.J. Keil

Irish Hills spineflower

Print Report

Taxon Summary

Chorizanthe aphanantha, commonly known as Irish Hills spineflower, is a annual herb in the Polygonaceae that is found only in California. It occurs within Chaparral (edges, openings), and Coastal scrub, growing at elevations from 100 to 370 meters. Chorizanthe aphanantha is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

Classification


Scientific Name:	Chorizanthe aphanantha K.M. Nelson & D.J. Keil
Common Name:	Irish Hills spineflower
Family:	Polygonaceae
Element Code:	PDPGN04110
USDA Plants Symbol:
Synonyms/Other Names:

Ecology and Life History


Lifeform:	annual herb
Blooming Period: Apr-Jun	Apr-Jun
Elevation:	100-370 (330-1215)
General Habitats:	Chaparral, Coastal scrub
Microhabitat:	Gravelly, Rocky, Serpentine
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.1
Global Rank:	G1
State Rank:	S1
State List:	None
Fed List:	None
Other Status:	BLM_S; SB_SBBG
CRPR Changes:	added to 1B.1 on 2019-06-12

Occurrence Data from the CNDDB


Total Occurrences:	3
Element Occurrence Ranks:
Excellent (A)	0
Good (B)	0
Fair (C)	0
Poor (D)	0
None (X)	0
Unknown (U)	3

Location


California Endemic: True
California Counties and Islands: Name (Code)
San Luis Obispo (SLO)
Quads: Name (Quad Code)
Pismo Beach (3512026), San Luis Obispo (3512036)

Threat List Data from the CNDDB


Threat List Total:	0
EOs with Threat Listed:	Total EOs	% of EOs
	0	%

Notes



Similar to and co-occurs with C. breweri; differentiated in having perianth 1.5-1.7 mm long (vs. 2-5 mm) and involucre green at flowering (vs. red to purple at flowering in C. breweri).
Threats:

Taxonomy:

Selected References

Proposed Addition to CRPR 1B.1, G1 / S1 (2019)

Madroño 65(4):184-191 (2018)

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 6 November 2025].