Poison hemlock
Conium maculatum
A highly poisonous biennial with finely divided foliage and clusters of white flowers. Its resemblance to members of the carrot family has led to dangerous mistakes.
- Family
- Apiaceae
- Regional status
- Introduced
- Habitat
- Roadsides & disturbed wet ground
- Safety
- Highly poisonous
A closer look.
UC IPM describes hairless foliage and hollow stems often marked with purple mottling. These are educational features, not a reliable checklist for safe collection. Poison hemlock occurs in disturbed ground, including ditch banks and roadsides. All parts should be treated as hazardous.
University of California Statewide IPM Program ↗ · National Capital Poison Center ↗
Compared with linked references on October 22, 2026. This is source verification, not independent expert review or an identification guarantee. Seasonal tags are approximate. Specimen maps show a selected historical subset.
Through the seasons
Spring and summer flowering is described by UC IPM. Toxic material may be present outside the flowering season.
Knowledge has a context.
Historical accounts are presented as attributed records, not endorsed practices, medical advice, or permission to harvest.
Historical narratives are withheld pending review. The current record prioritizes documented toxicity and dangerous confusion with food plants.
A record of where it was found.
Widely distributed in western North America and California’s disturbed, often moist low-elevation habitats.
Roadsides & disturbed wet ground
Northern California · Central California · Southern California
Historical collections are evidence of recorded locations, not a continuous range, current presence, abundance, native status, or confirmed identification. Unmapped places are not evidence of absence.
What this map includes
From the first 300 results returned by the stored GBIF query, 20 specimens met the coordinate and reuse filters; 280 were excluded. The query matched 769 records at retrieval. This subset is not random or exhaustive.
Records are labeled California, have coordinates, and lack GBIF geospatial-issue flags. We exclude known coordinate uncertainty above 25 km and use only CC0 or CC BY 4.0 records. 19 included records do not report coordinate uncertainty. A 0.25° cell is about 28 km north to south; it does not show an exact collecting site.
Matched taxon: Conium maculatum ↗.
Inspect the stored query ↗ · Download the attributed snapshot ↓
University of California Statewide IPM Program ↗ · National Capital Poison Center ↗
Data publishers & selected records
Dataset citations apply to the contributing specimens. The snapshot retains record IDs, original ownership, and reuse licenses; coordinates are generalized to a quarter-degree grid.
- University of British Columbia Herbarium (UBC) - Vascular Plant Collection ↗
PJ Lipsen L, Bucci P (2026). University of British Columbia Herbarium (UBC) - Vascular Plant Collection. Version 16.44. University of British Columbia. Occurrence dataset https://doi.org/10.5886/rtt57cc9 accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/publicdomain/zero/1.0/legalcode · accessed October 26, 2026
- UTEP Plants (Arctos) ↗
Mayfield-Meyer T, Zhuang V (2026). UTEP Plants (Arctos). Version 5.117. University of Texas at El Paso Biodiversity Collections. Occurrence dataset https://doi.org/10.15468/yhb6ky accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/publicdomain/zero/1.0/legalcode · accessed October 26, 2026
- SMMSH - Santa Monica Mountains & Simi Hills Herbarium of the National Park Service - Vascular Plant Collection ↗
Santa Monica Mountains National Recreation Area: National Park Service (2026). SMMSH - Santa Monica Mountains & Simi Hills Herbarium of the National Park Service - Vascular Plant Collection. Occurrence dataset https://doi.org/10.15468/637snr accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/publicdomain/zero/1.0/legalcode · accessed October 26, 2026
- MACF - MacFadden Herbarium, California State University Fullerton ↗
California State University, Fullerton (2026). MACF - MacFadden Herbarium, California State University Fullerton. Occurrence dataset https://doi.org/10.15468/1uvzxh accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- UCSB - University of California Santa Barbara Herbarium ↗
Cheadle Center for Biodiversity and Ecological Restoration (2026). UCSB - University of California Santa Barbara Herbarium. Occurrence dataset https://doi.org/10.15468/qpxmw0 accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/publicdomain/zero/1.0/legalcode · accessed October 26, 2026
- Digitalización y Sistematización de las Colecciones Biológicas Nacionales del Instituto de Biología, UNAM (Plantas vasculares) ↗
Sánchez Cordero Dávila V, Comisión nacional para el conocimiento y uso de la biodiversidad C (2026). Digitalización y Sistematización de las Colecciones Biológicas Nacionales del Instituto de Biología, UNAM (Plantas vasculares). Comisión nacional para el conocimiento y uso de la biodiversidad. Occurrence dataset https://doi.org/10.15468/9uut5l accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- R. L. McGregor Herbarium Vascular Plants Collection ↗
Bentley A, Morse C (2026). R. L. McGregor Herbarium Vascular Plants Collection. University of Kansas Biodiversity Institute. Occurrence dataset https://doi.org/10.15468/htptzr accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- Snake River Plain Herbarium (Boise State University, Idaho, USA) ↗
Smith J (2026). Snake River Plain Herbarium (Boise State University, Idaho, USA). Version 1.44. Consortium of Pacific Northwest Herbaria. Occurrence dataset https://doi.org/10.15468/nu8kw5 accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- Tropicos Specimens Non-MO ↗
Teisher J, Stimmel H (2026). Tropicos Specimens Non-MO. Version 1.122. Missouri Botanical Garden. Occurrence dataset https://doi.org/10.15468/rxbp4w accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- Arizona State University Vascular Plant Herbarium ↗
Arizona State University Biocollections (2026). Arizona State University Vascular Plant Herbarium. Occurrence dataset https://doi.org/10.15468/a2o8vy accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/licenses/by/4.0/legalcode · accessed October 26, 2026
- CAS Botany (BOT) ↗
Magnaghi E, Fong J (2026). CAS Botany (BOT). Version 157.669. California Academy of Sciences. Occurrence dataset https://doi.org/10.15468/7gudyo accessed via GBIF.org on 2026-10-26.
http://creativecommons.org/publicdomain/zero/1.0/legalcode · accessed October 26, 2026
View 20 included specimen records
- GBIF 4929357368 ↗ · 2023MACF - MacFadden Herbarium, California State University Fullerton · Mellifera R. Letterman · License
- GBIF 4923397541 ↗ · 2022CAS Botany (BOT) · White, Scott D. · License
- GBIF 2270549268 ↗ · 2018Arizona State University Vascular Plant Herbarium · Marc A. Baker; Michelle Cloud-Hughes · License
- GBIF 4068936393 ↗ · 2016Snake River Plain Herbarium (Boise State University, Idaho, USA) · Richard R. Halse · Boise State University, Snake River Plains Herbarium · License
- GBIF 4143391323 ↗ · 2016R. L. McGregor Herbarium Vascular Plants Collection · Richard R. Halse · License
- GBIF 4143392343 ↗ · 2016R. L. McGregor Herbarium Vascular Plants Collection · Richard R. Halse · License
- GBIF 1803151805 ↗ · 2016CAS Botany (BOT) · Howald, Ann · License
- GBIF 1426383285 ↗ · 2013CAS Botany (BOT) · Schneider, R.; Dugas, E.; Stern, J.; Wong, E. · License
- GBIF 3308732221 ↗ · 2010Digitalización y Sistematización de las Colecciones Biológicas Nacionales del Instituto de Biología, UNAM (Plantas vasculares) · G. K. Helmkamp; Mary Alice Barnes; Mary Jane Ganibe · Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO) · License
- GBIF 1426441463 ↗ · 2007CAS Botany (BOT) · Townesmith, Andrew; Meyer, Karen M. · License
- GBIF 4061097923 ↗ · 2007Tropicos Specimens Non-MO · Andrew Townesmith|Karen M. Meyer · Missouri Botanical Garden · License
- GBIF 2270252212 ↗ · 2006UCSB - University of California Santa Barbara Herbarium · McCleister, Deborah · License
- GBIF 5103574442 ↗ · 2005UTEP Plants (Arctos) · Collector(s): Andrew C. Sanders · License
- GBIF 6392073309 ↗ · 2004SMMSH - Santa Monica Mountains & Simi Hills Herbarium of the National Park Service - Vascular Plant Collection · Mike McGraw · National Park Service · License
- GBIF 1426269816 ↗ · 2004CAS Botany (BOT) · Sanders, A. C. · License
- GBIF 1988145915 ↗ · 2003University of British Columbia Herbarium (UBC) - Vascular Plant Collection · G. K. Helmkamp · The University of British Columbia · License
- GBIF 2270250777 ↗ · 2002UCSB - University of California Santa Barbara Herbarium · Gross, LeRoy; Fraga, Naomi; Williams, Steve · License
- GBIF 2270252848 ↗ · 2001UCSB - University of California Santa Barbara Herbarium · Magney, David; Wellonen, C. · License
- GBIF 4060965576 ↗ · 2000Tropicos Specimens Non-MO · John R. Stone|Sharon A. Bodine · Missouri Botanical Garden · License
- GBIF 2270251941 ↗ · 1999UCSB - University of California Santa Barbara Herbarium · Wellonen, Cher · License
Darker = more included records, not abundance
Boundary: US Census Bureau TIGERweb ↗ · locations generalized to 0.25° cells
Trace the record.
References are attached to specific parts of this record. A citation is a route to evidence; it is not a claim that every field has completed review.
- 01Poison Hemlock — Pest Notes ↗
University of California Statewide IPM Program
Supports: Toxicity, description, California habitat, and comparison with wild carrot.
- 02Get help online or by phone ↗
National Capital Poison Center
Supports: Immediate US poison exposure advice and 1-800-222-1222 contact.
- 03GBIF occurrence records & citation guidance ↗
GBIF Secretariat and contributing data publishers
Supports: Specimen occurrence snapshot. Each contributing dataset, DOI where available, record identifier, and license is retained in the downloadable map data.
- 04TIGERweb — States and Counties ↗
US Census Bureau
Supports: Generalized California state outline only; does not imply a species distribution.