Photo by Melody

PlantFiles: Poison Hemlock
Conium maculatum

Family: Apiaceae (ay-pee-AY-see-ee) (Info)
Genus: Conium (koh-NI-um) (Info)
Species: maculatum (mak-yuh-LAH-tum) (Info)

4 members have or want this plant for trade.


18-24 in. (45-60 cm)
24-36 in. (60-90 cm)
36-48 in. (90-120 cm)
4-6 ft. (1.2-1.8 m)
6-8 ft. (1.8-2.4 m)

36-48 in. (90-120 cm)

USDA Zone 5a: to -28.8 C (-20 F)
USDA Zone 5b: to -26.1 C (-15 F)
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)
USDA Zone 9a: to -6.6 C (20 F)
USDA Zone 9b: to -3.8 C (25 F)
USDA Zone 10a: to -1.1 C (30 F)
USDA Zone 10b: to 1.7 C (35 F)

Sun Exposure:
Full Sun
Sun to Partial Shade

All parts of plant are poisonous if ingested

Bloom Color:
White/Near White

Bloom Time:
Mid Summer


Other details:
May be a noxious weed or invasive

Soil pH requirements:
5.6 to 6.0 (acidic)
6.1 to 6.5 (mildly acidic)
6.6 to 7.5 (neutral)

Patent Information:

Propagation Methods:
By dividing rhizomes, tubers, corms or bulbs (including offsets)
From herbaceous stem cuttings
From seed; direct sow outdoors in fall
From seed; sow indoors before last frost
From seed; direct sow after last frost

Seed Collecting:
Bag seedheads to capture ripening seed
Allow seedheads to dry on plants; remove and collect seeds

Click thumbnail
to view:

By kennedyh
Thumbnail #1 of Conium maculatum by kennedyh

By melody
Thumbnail #2 of Conium maculatum by melody

By melody
Thumbnail #3 of Conium maculatum by melody

By melody
Thumbnail #4 of Conium maculatum by melody

By melody
Thumbnail #5 of Conium maculatum by melody

By melody
Thumbnail #6 of Conium maculatum by melody

By Late_Bloomer
Thumbnail #7 of Conium maculatum by Late_Bloomer

There are a total of 13 photos.
Click here to view them all!


1 positive
3 neutrals
2 negatives

Gardeners' Notes:

Negative NonniM On Apr 25, 2014, NonniM from Round Rock, TX wrote:

I rated my experience with this plant as negative because: in Texas, poison hemlock (conium maculatum) is classified as invasive, very poisonous and hard as the devil to eradicate by hand. We pulled every single plant last year but it was late in the season. The white flowers turn into the stickiest seed I've ever seen. The plants are back this year and I don't know how we will ever get rid of them! Any ideas?

Neutral Tabacum On Aug 4, 2010, Tabacum from Mantua, OH (Zone 5a) wrote:

This beautiful plant appeared at the corner of my acre
of flowers last year. It grew about 3 ft and was covered
with lacy foilage. I thought it must be pretty hardy to survive our 20 below winters here in Ohio. I decided to keep it to see what it would be. We live in a conservancy
district that consists of black Carlisle muckland. Our
fields flood every spring and I do lose a lot of plants.
This survived, and with the high heat we had this summer,
it grew to eight feet. I was stunned. It was beautiful.
I went online to this site and discovered this was a poison
hemlock. Thanks to all you people for putting your pictures on. I took the plant out before it went to seed.
Sent seeds to the landfill. The root I dug out was huge.
My memories will be in my pictures. We try to keep our
conservancy district plants natural to their habitat.

Negative frostweed On Dec 14, 2006, frostweed from Josephine, Arlington, TX (Zone 8a) wrote:

Poison Hemlock Conium maculatum is Naturalized to Texas and other States and is considered an Invasive plant in Texas.

Neutral dragon_lady2 On Dec 2, 2006, dragon_lady2 from Sapulpa, OK wrote:

Instead of looking at the leaves to determine if the plant is poison hemlock or queen anne's lace, observe the stem. Hemlock is smooth, has ribbing that runs the length of the plant much like celery only smoothly. Queen Anne's lace is prickly along the main stem. There are times when you won't see the red pin prick in the center of Queen Anne's lace flowers but the stem is either smooth and poisonous and that is hemlock or it is very prickly for queen anne's lace. If in doubt ever, stay away from it. I pull hemlock out always.

Neutral melody On May 25, 2005, melody from Benton, KY (Zone 7a) wrote:

I do not cultivate this plant, it grows wild in my area.

This is a tall plant, usually over 6', with many branches, usually a biennial. It produces a thick rosette of ferny leaves the first year, sends up a multi-branched stem the second that is covered in many umbels of white flowers.

It favors, waste places, weedy roadsides and damp woodland borders throughout the East except for Newfoundland and the Arctic. It is also seen in the West.

It is identified by the deeply toothed compound leaflets. The leaf veins run to the tips of the lobes or teeth, rather than into the notches between them.

As stated above, it is highly toxic and care should be taken when handling it and keep it from grazing farm animals.

Positive mesoto On Jul 15, 2003, mesoto from Crestview, FL wrote:

Poison hemlock is often found growing wild in marsh and waterside areas here in northeastern Florida. It's a hazard to anyone looking for wild carrots, parsley and the like because of its toxicity and resemblance to these plants. It was used by the greeks to put people to death (the dried roots were made into a toxic "tea")


This plant has been said to grow in the following regions:

Union Grove, Alabama
Golden, Colorado
Bartow, Florida
Kansas, Illinois
Benton, Kentucky
Joplin, Missouri
Plainfield, New Jersey
Roselle Park, New Jersey
South Plainfield, New Jersey
Walworth, New York
Wilsons Mills, North Carolina
Mantua, Ohio
Sapulpa, Oklahoma
Corbett, Oregon
Greencastle, Pennsylvania
Millersburg, Pennsylvania

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