Taxon Report
Cirsium hydrophilum (Greene) Jeps. var. hydrophilumSuisun thistle |
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Taxon Summary
Cirsium hydrophilum var. hydrophilum, commonly known as Suisun thistle, is a perennial herb in the Asteraceae that is found only in California. It occurs within Marshes and swamps, growing at elevations from 0 to 1 meters. Cirsium hydrophilum var. hydrophilum is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.Classification
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Scientific Name: |
Cirsium hydrophilum (Greene) Jeps. var. hydrophilum |
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Common Name: |
Suisun thistle |
| Family: | Asteraceae |
| Element Code: | PDAST2E1G1 |
| USDA Plants Symbol: | CIHYH |
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Synonyms/Other Names: |
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Ecology and Life History
| Lifeform: | perennial herb |
| Blooming Period: Jun-Sep | Jun-Sep |
| Elevation: | 0-1 (0-5) |
| General Habitats: | Marshes and swamps |
| Microhabitat: | |
| Microhabitat Details: |
Conservation Status
| CA Rare Plant Rank: | 1B.1 |
| Global Rank: | G2T1 |
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State Rank: |
S1 |
| State List: | None |
| Fed List: | FE |
| Other Status: | SB_CalBG/RSABG |
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CRPR Changes: |
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Occurrence Data from the CNDDB
| Total Occurrences: | 4 |
| Element Occurrence Ranks: | |
| Excellent (A) | 1 |
| Good (B) | 1 |
| Fair (C) | 1 |
| Poor (D) | 1 |
| None (X) | 0 |
| Unknown (U) | 0 |
| California Endemic: True | |
| California Counties and Islands: Name (Code) | |
| Solano (SOL) | |
| Quads: Name (Quad Code) | |
| Denverton (3812128), Fairfield South (3812221) | |
Threat List Data from the CNDDB
| Threat List Total: | 8 | |
| EOs with Threat Listed: | Total EOs | % of EOs |
| 4 | 100 % | |
| Foot traffic/trampling | 3 | 75% |
| Grazing | 3 | 75% |
| Non-native plant impacts | 3 | 75% |
| Hybridization | 2 | 50% |
| Improper burning regime | 1 | 25% |
| Non-native animal impacts | 1 | 25% |
| Altered flood/tidal/hydrologic regime | 1 | 25% |
| Feral pigs | 1 | 25% |
Notes
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Rediscovered in 1989 by N. Havlik on Grizzly Isl. in the Suisun Marsh; now known from two occurrences. Threatened by altered hydrology and competition from native and non-native plants. Potentially threatened by foot traffic and trampling by cattle. Protected in part at Grizzly Island WA and Peytonia Slough ER (both DFG). See Proceedings of the Academy of Natural Sciences of Philadelphia |
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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 27 June 2025].