Taxon Report

Centromadia parryi (Greene) Greene ssp. congdonii (Rob. & Greenm.) B.G. Baldwin

Congdon's tarplant

Print Report


Taxon Summary

Centromadia parryi ssp. congdonii, commonly known as Congdon's tarplant, is a annual herb in the Asteraceae that is found only in California. It occurs within Valley and foothill grassland, growing at elevations from 0 to 230 meters. Centromadia parryi ssp. congdonii is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

  Classification
Scientific Name:
 Centromadia parryi (Greene) Greene ssp. congdonii (Rob. & Greenm.) B.G. Baldwin
Common Name:
 Congdon's tarplant
Family: Asteraceae
Element Code: PDAST4R0P1
USDA Plants Symbol: CEPAC
Synonyms/Other Names:
  • Hemizonia parryi Greene ssp. congdonii (Rob. & Greenm.) Keck

Ecology and Life History
Lifeform: annual herb
Blooming Period: (Apr)May-Oct(Nov) (Apr)May-Oct(Nov)
Elevation: 0-230 (0-755)
General Habitats: Valley and foothill grassland
Microhabitat:
Microhabitat Details:

Conservation Status
CA Rare Plant Rank: 1B.1
Global Rank: G3T2
State Rank:
 S2
State List: None
Fed List: None
Other Status: BLM_S; SB_CalBG/RSABG
CRPR Changes:
  • changed from 1B.2 to 1B.1 on 2012-11-05

Occurrence Data from the CNDDB
Total Occurrences: 96
Element Occurrence Ranks:
   Excellent (A) 9
   Good (B) 16
   Fair (C) 32
   Poor (D) 13
   None (X) 15
   Unknown (U) 11

Location
California Endemic:  True
California Counties and Islands: Name (Code)
Alameda (ALA), Contra Costa (CCA), Monterey (MNT), San Luis Obispo (SLO), San Mateo (SMT), Santa Clara (SCL), Santa Cruz (SCR)*, Solano (SOL)*
Quads: Name (Quad Code)
Altamont (3712166), Arroyo Grande NE (3512025), Benicia (3812212)*, Byron Hot Springs (3712176), Calaveras Reservoir (3712147), Chualar (3612155), Diablo (3712178), Dublin (3712168), Gonzales (3612154), Hayward (3712261)*, Livermore (3712167), Los Gatos (3712128), Milpitas (3712148), Moss Landing (3612177), Mountain View (3712241), Natividad (3612165), Newark (3712251), Niles (3712158), Palo Alto (3712242), Palo Escrito Peak (3612144)*, Pismo Beach (3512026), Prunedale (3612176)(?), Salinas (3612166), San Jose East (3712137)*, San Jose West (3712138), San Leandro (3712262)*, San Luis Obispo (3512036), Santa Teresa Hills (3712127), Seaside (3612157), Soledad (3612143), Spreckels (3612156), Tassajara (3712177), Vine Hill (3812211), Walnut Creek (3712281)*, Watsonville East (3612186)*, Watsonville West (3612187)

Threat List Data from the CNDDB

Threat List Total: 18
EOs with Threat Listed: Total EOs % of EOs
74 77 %
Development 37 38%
Grazing 20 20%
Other 20 20%
Road/trail construction/maint. 15 15%
Non-native plant impacts 12 12%
Foot traffic/trampling 10 10%
Disking 9 9%
Agriculture 9 9%
Recreational use (non-ORV) 6 6%
Biocides 4 4%
ORV activity 4 4%
Vandalism/dumping/litter 2 2%
Waterway bank protection/maintenance 1 1%
Altered flood/tidal/hydrologic regime 1 1%
Erosion/runoff 1 1%
Hybridization 1 1%
Improper burning regime 1 1%
Military operations 1 1%

Notes
Severely threatened by development. Possibly threatened by grazing and non-native plants. A synonym of Hemizonia parryi ssp. congdonii in TJM (1993). See Botanical Gazette 22:169 (1896) for original description, and Novon 9:462-471 (1999) 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].