Poison hemlock
Discuss this plant with the guide — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.
Conium maculatum
Colorado List C — Manage widespread weeds. S16
Widespread and well established. Control is recommended by the state; local governments may require management. This is a management category, separate from danger ratings. Category source · What the lists mean.
Poisonous to people & animals. Native status, garden use and noxious-weed class are separate from toxicity. Exposure help.
Still researching this plant
This is a sourced working profile. The cited findings are available below. Independent botanical and veterinary review is pending. Uncertainty is not a finding that the plant is safe.
Three views of this plant
Photos are source-identified examples, not a complete identification key. Check leaves, stems, flowers and fruit together. Locations are not assumed to be in Colorado.
Krzysztof Ziarnek, Kenraiz · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
MPF · CC BY-SA 3.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Nicolas Ramirez · CC BY-SA 4.0
Photo source and identification
Original record · Original image
Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination.
Wikimedia server-resized derivative; no crop, color change, or generative editing. Gallery display preserves the full image; the catalog preview uses a CSS crop.
Recognize
Finely divided leaves, stems with purple spots, and white umbrella-like flower clusters. Often near streams, ditches, and pasture edges. S16
Plants & habitat
An introduced, colony-forming biennial. Garden judgment: exclude access and seek local management help once identification is confirmed. S16
People
All parts are poisonous. Do not eat or taste it to identify it. Suspected ingestion warrants immediate Poison Control advice. S16 S26
Dogs & cats
The county warning covers animals broadly. Treat suspected ingestion by a pet as urgent and contact a veterinarian. S16 S04
Other animals
Poisonous to livestock; do not use grazing as a control method. A List C designation does not indicate low toxicity. S16
Before taking action
Confirm the scientific name before removing a plant, changing animal access, or choosing treatment. An evidence gap means this review has not resolved the question. It does not mean safe. For listed weeds, consult your county weed program about the requirements for your location; follow the current label for any pesticide. S27
References
- S16 — Poison Hemlock, Jefferson County, Colorado. Accessed 2026-09-07T00:23:54+00:00. Locator: List C designation; General; Habitat; Vegetation; Flower.
- S26 — First aid guidelines, National Capital Poison Center. Accessed 2026-09-07T00:23:56+00:00. Locator: Poison center phone; emergency symptoms; do not induce vomiting.
- S04 — Milkweed, ASPCA Poison Control. Accessed 2026-09-07T00:23:52+00:00. Locator: Scientific Name; Toxicity; Clinical Signs; poison contact.