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)

Category:

Biennials

Height:

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)

Spacing:

36-48 in. (90-120 cm)

Hardiness:

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

Danger:

All parts of plant are poisonous if ingested

Bloom Color:

White/Near White

Bloom Time:

Mid Summer

Foliage:

Herbaceous

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:

Non-patented

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

Regional

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

Temple, Texas

show all

Gardeners' Notes:

1
positive
3
neutrals
3
negatives
RatingContent
Negative

On May 8, 2015, gardengranny792 from Fredonia, TX wrote:

I cannot imagine why anyone would propagate this plant for any reason. Toxic to animals and man, the flowers don't begin to justify doing anything with this plant. A coral snake is undeniably beautiful, but if you found one in your garden you'd most likely eradicate it, even though it is not nearly as toxic and invasive as hemlock.
Please carefully eradicate this pest and plant Queen Anne's lace or yarrow. Both more beautiful and useful to man.
I wish you had not given growing instructions here.

Negative

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

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 ... read more

Negative

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

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

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

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")