Poison Hemlock (Conium maculatum)

Common names:
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General Plant Information (Edit)
Plant Habit: Herb/Forb
Life cycle: Biennial
Sun Requirements: Full Sun to Partial Shade
Partial or Dappled Shade
Water Preferences: Mesic
Plant Height: 5 to 8 feet
Leaves: Deciduous
Other: basal rosette first year/1 to 16 inches long/1 leaf per node, alternate, fern-like
Flowers: Showy
Other: umbrella shaped clusters
Flower Color: White
Bloom Size: Under 1"
Flower Time: Spring
Inflorescence Height: up to 8 feet
Underground structures: Taproot
Toxicity: Leaves are poisonous
Roots are poisonous
Fruit is poisonous
Other: Juice was given to Socrates (famous Greek philosopher), he died.
Propagation: Seeds: Self fertile
Other info: One plant may have 38000 seeds.
Pollinators: Various insects
Containers: Not suitable for containers
Conservation status: Least Concern (LC)

Conservation status:
Conservation status: Least Concern

Photo gallery:

Posted by valleylynn (Dallas, OR - Zone 8b) on May 27, 2012 5:14 PM

Poison hemlock is a perennial member of the Umbelliferae (parsley) family. The plants are up to 6 feet tall with smooth, hollow stems covered with purple spots. Leaves are finely divided, resembling those of parsley or carrots. Crushed leaves have a mouse-like odor. The plant is sometimes confused with wild carrot (Daucus carota, Queen Anne's lace). There is a large white to pale yellow taproot.

Geographic range: poison hemlock grows on fertile, moist soils across the United States in locations such as woodlots, fence rows and waste areas.

Toxic principle: Coniine and related pyridine-type alkaloids are present in the root, young plants and seeds. As plants mature, the foliage loses alkaloid content, but the seeds accumulate the alkaloid. Hay can retain toxicity.

Toxicity: The whole green plant is toxic at dosages of approximately 1% of body weight.

Poison hemlock can also cause birth defects in ruminants and swine, with cattle and swine more susceptible than sheep and goats. The most often reported birth defects are cleft palate and spinal abnormalities. The gestational ages that have been associated with birth defects are: for goats, days 30 through 60; for cattle, days 40 through 70; for pigs, days 30 through 60. The birth defects resemble those seen with lupine, with lupine being the more dangerous plant.

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Posted by ILPARW (southeast Pennsylvania - Zone 6b) on Mar 11, 2018 7:38 PM

It is sort of pretty, but it is a horrible invasive weed from Europe that is poisonous and full of bad juice. Unfortunately, it is a common weed in the Eastern & Midwestern US. Wearing lots of clothing and gloves, I have wacked it down with a sickle and even pulled some up with their taproots and I have not suffered any ill effects, but other people are more sensitive to get rashes near this plant. It pops up fairly early in the spring, but fortunately it goes dormant in late summer and fall with the foliage turning brown and falling down.

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Posted by Bonehead (Planet Earth - Zone 8b) on Mar 26, 2018 4:24 PM

Class B noxious weed in Washington state (do not allow to spread). Colonizes roadsides, vacant lots, pastures, waterways. Wear protection when removing this plant, all parts are toxic, even after it has dried. Best to dispose of in the trash.

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Posted by jmorth (central Illinois) on Nov 25, 2015 5:56 PM

The infamous plant Socrates ingested in 399 BC that caused his death.

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Discussion Threads about this plant
Thread Title Last Reply Replies
Does anyone know what plant this is? by Toni Apr 30, 2018 12:00 PM 3
Poison hemlock? by fahte Apr 13, 2018 8:07 AM 7
What is this? by Bluebird32 Apr 8, 2018 5:27 AM 5
Flower ID help, please! by Shoshi Jun 15, 2017 9:15 AM 7
These "weeds" are turning into trees, and I'm going to let them! by eturner99 May 1, 2017 7:07 PM 17
Looking for identification - BC by shmaveyea Apr 26, 2017 2:32 PM 6
What is this? by SamVT Sep 27, 2016 6:26 PM 4

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