Plant guide

Poison hemlock.

Conium maculatum

Pronounced KOH-nee-um mack-yoo-LAY-tum

Also known as Carrot-fern, Deadly Hemlock, Fool's-parsley

Poison hemlock is a highly toxic biennial plant often found in disturbed areas and along roadsides. It is famous for its historical use as a lethal poison. You should avoid touching or ingesting this plant entirely.

At a glance

Care level: Easy
Plant type: Biennial herbaceous plant
Light: Full sun to partial shade
Indoor light: Direct sun
Water: Every 3 to 7 days
Mature size: 6 to 10 feet
Growth rate: Fast

Care

This plant is considered a dangerous invasive weed and should not be cultivated in home gardens. If you find it on your property, wear gloves and protective clothing to remove it before it sets seed. Watch for skin irritation after any contact with the foliage.

Watering: It prefers consistently moist soil but can tolerate short dry spells.
Feeding: It does not require fertilization as it thrives in most soil conditions.
Pruning: Remove flower heads before they produce seeds to prevent further spread.
Repotting: It is not recommended to keep this plant in containers due to its size and toxicity.
Soil: Moist, fertile, well drained soil
Soil pH: 6.0 to 8.0

Safety

Pets: This plant is extremely poisonous to both cats and dogs if ingested.

How to identify it

Purple blotches on smooth stems
Finely divided fern like leaves
Small white flowers in umbels
Taproot resembles a parsnip

Science

Family: Apiaceae
Genus: Conium
Order: Apiales
Class: Magnoliopsida

Taxonomy resolved against GBIF.

Also in

Plants toxic to cats and dogs

Is your poison hemlock looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

Get the app

This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.