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Hemlock seeds

Exotic Species: Poison Hemlock

Native to Europe, western Asia, and North America, poison hemlock (Conium maculatum) is now naturalized in almost every state in the United States. It was introduced in the 1800s as a garden plant, marketed as being a “winter fern”. Poison hemlock is highly poisonous to humans and animals. It can acts as a pioneer species and quickly colonized disturbed sites. Infestations occur along roadsides, field margins, ditches, marshes, meadows, and low-lying areas, but poison hemlock prefers shaded areas with moist soil.

Map of poison hemlock distribution from the USDA PLANTS database (https://plants.usda.gov/java/profile?symbol=coma2).

Description

Poison hemlock is a highly toxic biennial with the musty, unpleasant odor associated with alkaloids. It grows two to ten feet tall. The stems are ribbed and hollow with purplish streaks or splotches. Poison hemlock reproduces by seeds that fall near the plant and disperse via fur, birds, water, and, to a limited extent, wind. Most seeds fall from September through December, but they can fall as late as the end of February. The seeds germinate in the fall, but the plant usually does not produce flowers until the second spring.

Leaves
The leaves have some resemblance to ferns. They are opposite and compound, with the leaflets divided into narrow segments. When crushed, the leaves emit a rank odor.

Poison hemlock leaves are pinnately compound (left), poison hemlock stems have purple stripes or splotches (middle), and poison hemlock plants after flowering (right).

Left: © Robert Vidécki; Middle and right: Bonnie Million / NPS

Flowers and Fruits
The small, white or yellowish flowers have five petals that bloom above the ovary. The flowers are borne in many umbrella-shaped clusters at the end of the flower stalks. Underneath each cluster are four to six brown bracts. The fruit is egg-shaped in outline, with distinctive wavy ribs on the surface. It is composed of two dry halves, each with one seed, that eventually separate from each other. The fruit is 2-3 mm wide.

Etymology

Co’nium is derived from the ancient Greek name coneion, meaning hemlock. Macula’tum means spotted, referring to purple splotches on the stems of leaves or on petals.

Ethnobotany

Poison hemlock is highly toxic. Ancient Greeks used poison hemlock to execute prisoners—Socrates being the most famous example.

Similar Species

Poison hemlock looks similar to wild carrot (Daucus carota), wild parsnip (Pastinaca sativa), and water hemlock (Cicuta maculata). Wild carrot and wild parsnip do not have purple mottling on their stems. In addition, wild carrot has a hairy stem. Water hemlock does have purple mottling and hairless stems, but unlike poison hemlock, it has a cluster of fleshy taproots at the base.

Control Methods

Possible control methods are explained at these websites:

References

Arizona Wildlands Invasive Plant Working Group. 2004. Conium maculatum Plant Assessment Form.

Cardina, J., C. Herms, T. Kock, and T. Webster. No date. Poison hemlock in Ohio Perennial and Biennial Weed Guide. Ohio Agricultural Research and Development Center Extension. Available at http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=550 (accessed 22 March 2010).

Charters, M. L. 2009. California plant names: Latin and Greek meanings and derivations. Available at http://www.calflora.net/botanicalnames (accessed 22 March 2010).

Constance, L. 1993. Conium maculatum in Hickson, J. C., editor. The Jepson Manual: Higher plants of California. University of California Press, Berkeley, CA.

Drewitz, J. 2000. Conium maculatum in Bossard, C. C., J. M. Randall, and M. C. Hoshovsky, editors. Invasive plants of California’s wildlands. University of California Press, Berkeley, CA. Available at http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport. [email protected]=32&surveynumber=182.php (accessed 22 March 2010).

Pitcher, D. 1989. Conium maculatum in Element Stewardship Abstracts. The Nature Conservancy, Arlington, VA. Available at http://www.imapinvasives.org/GIST/ESA/esapages/documnts/conimac.pdf.

Prepared by Kelly Reeves, Southern Colorado Plateau Network Inventory and Monitoring Program, 2010.

Poison Hemlock Going to Seed

Poison hemlock (Conium maculatum) is among the most deadly plants in North America. This non-native invasive weed contains highly toxic piperidine alkaloid compounds, including coniine and gamma-coniceine, which cause respiratory failure and death when ingested by mammals.

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TOXICITY:

Poison hemlock is native to North Africa and Eurasia including Greece. It’s the plant behind Socrates’ famous last words, “I drank what?” Or, maybe it was, “don’t try this at home.” Just kidding. In fact, it was the plant used to poison Socrates and thanks to Plato’s Phaedo, his actual last words are known and involved sacrificing a rooster to Asclepius. Their exact meaning has been debated by scholars for centuries … which is why I like my versions better.

The roots are more toxic than the leaves and stems; however, all parts of the poison hemlock plant including the seeds should be considered dangerous. The toxins cannot seep through our skin. Poison hemlock toxins must be ingested or enter through the eyes, cuts, or other openings to cause poisoning. Another possible mode of entry is through inhalation which is why plants should never be burned. The structural formula for coniine is very similar to nicotine; the two are chemical cousins. It’s reasonable to assume that coniine can be carried by smoke into lungs just like nicotine. However, coniine is much more toxic compared to nicotine.

CONTROL:

Poison hemlock is a biennial weed: the first year is spent as a basal rosette and the second year as an erect, towering flowering plant that can measure 6-10′ tall. It is a prolific seed producer. Flowering plants are now turning brown with the seed is rapidly maturing in southern Ohio. This mean management options are limited. The dying plants aren’t susceptible to herbicides and mowing or tilling will not destroy the seed. At this point, the best option is to wait until spring and target the basal rosettes as well as new plants from the current seed crop with selective or non-selective post-emergent herbicides including glyphosate (e.g. Roundup).

APHID INFESTATION:

On an interesting side note, while photographing poison hemlock plants that are going to seed, I came across several plants heavily infested with aphids that had attracted a large population of Multicolored Asian Lady Beetles (MALB). I was surprised that the aphids and their predators were doing so well. I’ve tentatively identified the aphids as the Fennel Aphid (Hyadaphis foeniculi) which along with a few other species is capable of sucking sap from poison hemlock without going the way of Socrates. However, I remain surprised that MALB is able to chow-down on the aphids with immunity. Are the aphids rapidly detoxifying the hemlock sap? Are they only showing up when hemlock plants are dying and possibly less toxic? Perhaps all will be revealed if we heed Socrates’ last words and sacrifice a rooster to Asclepius.

Hemlock

California Fern, Carrot Weed, Cicuta, Ciguë, Ciguë d’Athènes, Ciguë Officinale, Ciguë de Socrate, Ciguë Tachetée, Conium, Conium Maculata, Conium maculatum, Grande Ciguë, Mort aux Oies, Nebraska Fern, Poison Fool’s Parsley, Poison-Hemlock, Spotted Hemlock, Tsuga, Vicaire, Wild Carrot.

Overview

Hemlock is a very poisonous plant. In fact, all parts of the plant are toxic. Hemlock is most poisonous during the early stages of growth in the spring, but it is dangerous at all stages of growth. The poisons in hemlock are so deadly that people have died after eating game birds that had eaten hemlock seeds.

Hemlock is native to Europe and western Asia and was introduced into North America as an ornamental plant. It is frequently found in the US and southern Canada. Hemlock typically grows near fences, roadsides, ditches, abandoned construction sites, pastures, crops, and fields, where it can be confused with harmless plants. Accidental poisonings have occurred when people mistook the root for parsnip, leaves for parsley, or seeds for anise.

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Despite serious safety concerns, hemlock leaves, root, and seeds are used to make medicine. It is used for breathing problems including bronchitis, whooping cough, and asthma; and for painful conditions including teething in children, swollen and painful joints, and cramps.

Hemlock is also used for anxiety and mania. Other uses include treatment of spasms tumors, skin infections, epilepsy, Parkinson’s disease, Sydenham’s chorea, and bladder infections.

Hemlock has also been used to reverse strychnine poisoning.

How does it work?

Hemlock contains poisons that affect the transmission of nerve impulses to muscle. Death occurs by respiratory failure.

SLIDESHOW

Uses & Effectiveness

Insufficient Evidence to Rate Effectiveness for.
  • Anxiety.
  • Muscle spasms.
  • Teething in children.
  • Cramps.
  • Mania.
  • Bronchitis.
  • Whooping cough.
  • Asthma.
  • Other conditions.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Side Effects

All parts of hemlock, including seeds, flowers, and fruits, are UNSAFE. Hemlock is so poisonous it can cause death. If someone takes hemlock, he or she should get immediate medical attention. Side effects and toxicities include increased saliva, burning of the digestive tract, drowsiness, muscle pain, rapid swelling and stiffening of muscles, kidney damage, rapid breakdown of muscle tissue and release of muscle tissue byproducts into the blood, rapid heart rate followed by a decreased heart rate, loss of speech, paralysis, unconsciousness, heart, lung, and kidney failure, and death.

QUESTION

Special Precautions & Warnings

It is UNSAFE for anyone to use hemlock, but people with the following conditions are especially likely to experience unwanted side effects.

Children: Use of hemlock is UNSAFE and can be fatal, especially in children. Children can be poisoned by even small amounts of hemlock. Some children have died after eating leaves or using hollow hemlock stems as peashooters, flutes, or whistles. Hemlock should not be used for treating pain in children due to teething.

Pregnancy and breast-feeding: Use of hemlock is UNSAFE and can be fatal.

Dosing

The appropriate dose of hemlock depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for hemlock. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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