Taxon Report
Holocarpha macradenia (DC.) GreeneSanta Cruz tarplant |
 © 2011 Dylan Neubauer |
Taxon Summary
Holocarpha macradenia, commonly known as Santa Cruz tarplant, is a annual herb in the Asteraceae that is found only in California. It occurs within Coastal prairie, Coastal scrub, and Valley and foothill grassland, growing at elevations from 10 to 220 meters. Holocarpha macradenia is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.Classification
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Scientific Name: |
Holocarpha macradenia (DC.) Greene |
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Common Name: |
Santa Cruz tarplant |
| Family: | Asteraceae |
| Element Code: | PDAST4X020 |
| USDA Plants Symbol: | HOMA |
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Synonyms/Other Names: |
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Ecology and Life History
| Lifeform: | annual herb |
| Blooming Period: Jun-Oct | Jun-Oct |
| Elevation: | 10-220 (35-720) |
| General Habitats: | Coastal prairie, Coastal scrub, Valley and foothill grassland |
| Microhabitat: | Clay (often), Sandy |
| Microhabitat Details: |
Conservation Status
| CA Rare Plant Rank: | 1B.1 |
| Global Rank: | G1 |
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State Rank: |
S1 |
| State List: | CE |
| Fed List: | FT |
| Other Status: | SB_CalBG/RSABG; SB_UCBG |
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CRPR Changes: |
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Occurrence Data from the CNDDB
| Total Occurrences: | 37 |
| Element Occurrence Ranks: | |
| Excellent (A) | 1 |
| Good (B) | 4 |
| Fair (C) | 8 |
| Poor (D) | 5 |
| None (X) | 16 |
| Unknown (U) | 3 |
| California Endemic: True | |
| California Counties and Islands: Name (Code) | |
| Alameda (ALA)*, Contra Costa (CCA)*, Marin (MRN)*, Monterey (MNT), Santa Cruz (SCR) | |
| Quads: Name (Quad Code) | |
| Briones Valley (3712282), Felton (3712211), Hayward (3712261)*, Laurel (3712118), Oakland West (3712273)*, Prunedale (3612176), Richmond (3712283)*, San Rafael (3712285)*, Santa Cruz (3612281), Soquel (3612188), Watsonville East (3612186), Watsonville West (3612187) | |
Threat List Data from the CNDDB
| Threat List Total: | 10 | |
| EOs with Threat Listed: | Total EOs | % of EOs |
| 29 | 78 % | |
| Development | 19 | 51% |
| Grazing | 12 | 32% |
| Non-native plant impacts | 11 | 29% |
| Other | 4 | 10% |
| Foot traffic/trampling | 4 | 10% |
| Road/trail construction/maint. | 3 | 8% |
| Recreational use (non-ORV) | 2 | 5% |
| ORV activity | 2 | 5% |
| Mining | 1 | 2% |
| Agriculture | 1 | 2% |
Notes
| All extant CCA Co. occurrences (465B, 466A) are introduced; nearly half have failed. Last remaining natural population in the S.F. Bay Area extirpated by development in 1993. Seriously threatened by urbanization, agriculture, non-native plants, and lack of appropriate ecological disturbance. See Fremontia 5(4):15-16 (1978) for species account. |
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Threats: |
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Taxonomy: |
Citation
California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 2 November 2025].