Conium maculatum (Poison Hemlock)
| Also known as: | |
|---|---|
| Genus: | Conium |
| Family: | Apiaceae (Carrot) |
| Life cycle: | biennial |
| Origin: | Europe |
| Status: |
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| Habitat: | sun; moist disturbed soil; shores, river banks, roadsides, fields, along railroads, woodland edges |
| Bloom season: | June - August |
| Plant height: | 3 to 10 feet |
| Wetland Indicator Status: | GP: FACW MW: FACW NCNE: FACW |
| MN county distribution (click map to enlarge): |  |
| National distribution (click map to enlarge): |  |
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Detailed Information
Flower: 
![[photo of flowers]](/udata/r9ndp23q/white/poison-hemlock_0701_085312.jpg)
Flat clusters (umbels) at the tips of branching stems and arising from upper leaf axils. Umbels are 3 to 6 inches across, made up of up to 20 smaller clusters (umbellets), each with 20+ 1/8-inch white flowers. Flowers have 5 petals, 5 white stamens and a greenish white center. Around the base of both umbels and umbellets are 4 to 6 short bracts that are lance to egg-shaped, pointed at the tip and hairless.
Leaves and stem:
![[photo of leaves]](/udata/r9ndp23q/white/poison-hemlock_0701_085625.jpg)
Leaves are alternate, 2 to 4 times compound, up to 16 inches (20 to 40 cm) long and wide, generally triangular in outline, becoming smaller as they ascend the stem. Leaflets are divided and fern-like, to 2 inches long and 1 inch wide.
![[photo of stem]](/udata/r9ndp23q/white/conium-maculatum-poison-hemlock_0627_135252.jpg)
Stems are much branched and light green or purple tinged, covered in purple spots. Leaves and stems are all hairless.
Fruit:
![[photo of developing fruit]](/udata/r9ndp23q/white/poison-hemlock_0713_095103.jpg)
Fruits are egg-shaped, slightly flattened, up to 1/8 inch (2 to 3 mm) long, with rows of bumpy or wavy ridges. It splits into 2 seeds.
Notes:
When we first documented this species in 2010, there were only 3 reports of it in the entire state, the first from Kittson County in 1992, the next two in 2009—ours in Ramsey County followed by one in Martin County. When I submitted our specimen to the herbarium, I recall the curator commenting that it was a interesting find but should be eradicated, so at least one person was aware of its potential. The county did treat the population but I don't know if it was actually eradicated since the railroad fenced the area off and I can no longer access it.
No matter. A few years later dozens more reports of it started coming in across the entire southern part of the state and it's now moving north, primarily along transportation corridors and waterways. Statewide eradication seems pretty unlikely at this point. The MN Dept. of Agriculture designated it a Prohibited Control Noxious Weed in 2018, which means that, at a minimum, it must be controlled in a way that prevents its spread by seed or vegetative means. It's a biennial, a single plant can produce 30,000+ seeds, and dealing with the seed bank will likely be a years-long battle. Good luck.
All parts of Poison Hemlock are deadly poisonous. This plant is easy to distinguish from other members of the carrot family by the feathery, triple compound leaves and purple spotted stem. The native Water Hemlock (Cicuta maculata) is somewhat similar, but its leaves are not so finely divided and leaflets have a unique vein pattern, where veins terminate in the notch of teeth rather than at the tips. While some other members of the Carrot family (both native and not) have white flowers and similarly divided, fern-like leaflets, most are shorter, not much more than 3 feet tall, and may be hairy, where Poison Hemlock is hairless and is typically at least 5 feet tall at maturity.
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More photos
Poison Hemlock plant
Poison Hemlock along a railroad
Poison Hemlock establishing at Beaver Creek Valley State Park
Poison Hemlock propping up invasive Hops along the Root River
more leaves
stems from the previous year
Poison Hemlock plant
Poison Hemlock along a railroad
Poison Hemlock establishing at Beaver Creek Valley State Park
Poison Hemlock propping up invasive Hops along the Root River
more leaves
stems from the previous year Photos by K. Chayka taken in Fillmore, Houston and Ramsey counties.
Comments
Have you seen this plant in Minnesota, or have any other comments about it?
on: 2011-06-04 13:48:01
Found on both sides of the path leading to Marnie St from the southwest corner of the park, a couple hundred feet from the street.
on: 2011-06-18 12:42:54
Based on the images you sent, I would say what you found was Not poison hemlock after all, but sweet cicely. Many members of the carrot family have similar leaves, i.e. deeply divided and a bit feathery. Queen Ann's lace and Japanese hedge parsley are others. Looking at various plant parts and paying attention to small details can help narrow down an ID.
on: 2012-03-24 11:02:32
Chayka is right about them being sweet cicely and not poison hemlock one easy way to identify this plant is its mouse urine like smell
on: 2015-07-01 12:57:29
I believe I've located this plant on the north side of Lake Shady along 5th ST. N.W. The approximate size of the patch is 10' x 10' I have pics if you'd like to confirm my findings. Zed
on: 2015-07-05 10:00:38
Zed, there are a number of carrot species with similar flowers and growth habits. We prefer you post pictures on our Facebook page if possible, that way others can learn from it, too.
on: 2017-07-02 16:01:34
Katy, thank you for your comments above. I was trying to figure out a new plant that was showing up in our yard (St. Paul) this year. Looking at my wildflower guide, it seemed to be poison hemlock. But then I checked your website and figured out that it's Japanese Hedge Parsley. I will pull it out.
on: 2017-07-07 16:16:42
I found and took pictures of several suspect plants on the walking paths around Rosemount High School. I believe this to be Poison Hemlock.
on: 2017-07-07 16:38:40
John K, while poison hemlock is rapidly spreading in MN, it is not the only non-native white carrot found in disturbed areas such as along paths. Poison hemlock has more recently been seen traveling along waterways, though it is also found along transportation corridors such as railroad rights-of-way. More common in the Metro area is Torillis japonica, Japanese hedge-parsley, which is becoming common in wooded parks.
Poison hemlock is quite robust, growing over 6 feet tall with a smooth, stout, purple spotted stem, hairless leaves and hairless, ribbed seeds. Japanese hedge-parsley is 3-4 feet tall with a hairy stem, hairy leaves, and fruit with hooked hairs.
on: 2017-08-03 19:00:31
Along the St. Louis River trail near Perch Lake in far west Duluth. Also on state or county forest land southwest of Hwy 23 near Hwy 18 in the Wrenshall area. In addition, some very large plants in there look like Giant Hogweed. There are also a few small p. hemlock plants growing on a trail off Hwy 210 N/NW of Hwy 23.
on: 2017-08-04 17:51:16
Susan, there are no confirmed occurrences of giant hogweed in Minnesota. The common cow parsnip (Heracleum lanatum)is often mistaken for giant hogweed and that is more likely what you found. Poison hemlock is being tracked in MN. You can open an account and post your finding at EDDMapS but you must include photos that can confirm it is what you think it is. Images showing the finely divided leaves and purple-spotted stem are best. There have been quite a number of mid-IDs for these plants. Confirmation is necessary.
on: 2018-04-26 14:35:52
found along County round 3 between Janesville and Waldorf MN last summer/Fall. Lots of it. Waseca County.
on: 2018-04-26 16:01:00
Carmen, we discovered poison hemlock is starting to run rampant in southeast and south-central MN. There are vast populations traveling along the Root River in Fillmore County. It seems there is no stopping it now. :-(
on: 2018-12-16 19:00:10
I seem to recall seeing some in Duluth along the boardwalk. This was in the late 2000's or early 2010's. I saw the plant growing in abundance in Missouri more recently and the growth form, purple mottling of the stem, leaves, etc. all were exactly what I remembered seeing in Duluth.
on: 2022-07-28 09:53:56
Found a patch along some railroad tracks just north of Highway 14 in northwest Rochester.
on: 2024-09-07 19:59:18
Found along the Paul Bunyan trail, abundant on west side of trail from Jenkins through pine river. Found in wetter areas along ditch.