Taxon Report
Horkelia tenuiloba (Torr.) Graythin-lobed horkelia |
 © 1994 Doreen L. Smith |
Taxon Summary
Horkelia tenuiloba, commonly known as thin-lobed horkelia, is a perennial herb in the Rosaceae that is found only in California. It occurs within Broadleafed upland forest, Chaparral, and Valley and foothill grassland, growing at elevations from 50 to 500 meters. Horkelia tenuiloba is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.Classification
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Scientific Name: |
Horkelia tenuiloba (Torr.) Gray |
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Common Name: |
thin-lobed horkelia |
| Family: | Rosaceae |
| Element Code: | PDROS0W0E0 |
| USDA Plants Symbol: | HOTE2 |
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Synonyms/Other Names: |
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Ecology and Life History
| Lifeform: | perennial herb |
| Blooming Period: May-Jul(Aug) | May-Jul(Aug) |
| Elevation: | 50-500 (165-1640) |
| General Habitats: | Broadleafed upland forest, Chaparral, Valley and foothill grassland |
| Microhabitat: | Mesic, Openings, Sandy |
| Microhabitat Details: |
Conservation Status
| CA Rare Plant Rank: | 1B.2 |
| Global Rank: | G2 |
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State Rank: |
S2 |
| State List: | None |
| Fed List: | None |
| Other Status: | BLM_S; SB_CalBG/RSABG |
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CRPR Changes: |
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Occurrence Data from the CNDDB
| Total Occurrences: | 27 |
| Element Occurrence Ranks: | |
| Excellent (A) | 3 |
| Good (B) | 4 |
| Fair (C) | 6 |
| Poor (D) | 0 |
| None (X) | 0 |
| Unknown (U) | 14 |
| California Endemic: True | |
| California Counties and Islands: Name (Code) | |
| Marin (MRN), Mendocino (MEN), Sonoma (SON) | |
| Quads: Name (Quad Code) | |
| Annapolis (3812363), Bolinas (3712286), Camp Meeker (3812248), Dos Rios (3912363), Duncans Mills (3812341), Geyserville (3812268), Gualala (3812375), San Rafael (3712285), Sebastopol (3812247), Sonoma (3812234), Willis Ridge (3912353) | |
Threat List Data from the CNDDB
| Threat List Total: | 9 | |
| EOs with Threat Listed: | Total EOs | % of EOs |
| 12 | 44 % | |
| Road/trail construction/maint. | 5 | 18% |
| Agriculture | 4 | 14% |
| Development | 4 | 14% |
| Foot traffic/trampling | 3 | 11% |
| Grazing | 1 | 3% |
| Non-native plant impacts | 1 | 3% |
| Recreational use (non-ORV) | 1 | 3% |
| Disking | 1 | 3% |
| Biocides | 1 | 3% |
Notes
| Historical occurrences need field surveys. Threatened by development. Possibly threatened by foot traffic, trail maintenance, logging, and non-native plants. See Report of the Pacific Railroad Expedition 4(5):84 (1857) for original description, and Systematic Botany 18(1):137-144 (1993) for taxonomic treatment. |
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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 19 November 2025].