Conium maculatum is better known by its common names hemlock, wild hemlock, and of course poison hemlock. Because despite the fact that their leaves resemble the tasty parsley you might sprinkle over your pasta or add to your salads, all parts of this pretty plant are indeed rather poisonous, poison hemlock is also sometimes called fool’s parsley.
Poison hemlock belongs to the Apiaceae botanical family of flowering plants, making it a distant relative of fennel, carrots, parsley, and dill, as well as the also severely poisonous giant hogweed. The genus Conium has six officially recognized species.
Poison hemlock is native to Europe, specifically the Mediterranean region, but is now prolific in much of the UK as well and has become naturalized to the United States, too.
There’s no denying that Conium maculatum is a beautiful plant. The charming and delicate white flowers, which grow in abundant clusters that resemble the shape of an umbrella, are their most aesthetically-pleasing feature.
However, due to the severe poison profile, poison hemlock isn’t a plant you should want around in your garden, sadly. This weedy plant is quite hard to eradicate, but with the right steps, you can get it under control.
About Poison Hemlock
- 1 About Poison Hemlock
- 2 Poison Hemlock Features: An Overview
- 3 What Are the Symptoms of Hemlock Poisoning?
- 4 What Not to Do With Poison Hemlock
- 5 How to Get Rid of Poison Hemlock
- 5.1 Manually Removing Poison Hemlock From Your Garden
- 5.2 Mechanical Ways to Control Poison Hemlock
- 5.3 Using Herbicides to Kill Poison Hemlock
- 5.4 Biological Control: Poison Hemlock Moths
- Poison hemlock is a herbaceous biennial with complex deep green compound leaves that taper into a single tip. Its beautiful flower clusters are poison hemlock’s most striking feature. The flowers are usually white, but can also be pink.
- This poisonous plant is native to Europe, and was originally brought to the Americas in the nineteenth century, when it was originally sold as a winter fern. Poison hemlock has not been too much of a concern historically, but has recently began spreading prolifically in nearly all states, prompting the National Park Service and numerous news outlets to publish warnings about the plant.
- Conium maculatum resembles Queen Anne’s Lace (Daucus carota) which belongs to the same family quite closely. If you are not certain which of the two plants you are looking at, we would strongly recommend that you look at pictures of all parts of both plants to differentiate them. Do not rely on written descriptions of the plant’s features.
- Poison hemlock is in no way related to “hemlock” (Tsuga canadensis) and similar species — these coniferous trees are an entirely different species.
- The genus Conium was appropriately named — the Greek word from which it originates, koneios, means spinning or whirling — because eating any part of the plant can give you vertigo. Because the fact that ingesting any part of this plant is extremely dangerous, not just to humans but to all mammals and even many animals that aren’t mammals, we’ll deal with the potential consequences of hemlock poisoning, and what to do if you suspect a person or pet has eaten it, in a separate section.
- Because poison hemlock thrives in poorly-draining, soggy, soil, the plant can usually be found growing on waterlogged wastelands, along roads, and in ditches. In the US, this has become a particular problem in the midwest, which has been subjected to wet spring periods that poison hemlock loves to capitalize on. Conium maculatum flowers during the summer, after which the plant releases tens of thousands of seeds. These are, many people have already been warned, easy to scatter when mowing the lawn, causing the highly invasive plant to begin thriving in your garden.
- All plants are beautiful in their own way, and we don’t want to only say negative things about this beautiful plant that so many people are so desperate to get rid of. On the upside, poison hemlock attracts and supports some rare butterfly and moth species. Poison hemlock moths and silver-ground carpet moths depend on this plant, as their larvae feed on it.
- The fact that even small amounts of poison hemlock can be deadly greatly inspired Shakespeare and John Keats, and hemlock is even mentioned in the Bible.
Poison Hemlock Features: An Overview
A word of warning — although written descriptions of a plant’s features can be helpful, there are some other plants, notably parsley and Queen Anne’s Lace, that look quite a bit like poison hemlock. To identify poison hemlock with the greatest degree of certainty, you would be advised to look at pictures, examining all physical characteristics closely.
- Conium maculatum is a herbaceous perennial with an upright growth habit and vibrant green leaves, charming white flower clusters, and a fleshy taproot.
- These large flowering plants can grow to be five to eight feet (one and a half to two and a half meters) tall, and do not have a very wide spread.
- The shiny compound leaves of the poison hemlock plant have a vibrant green color. Arranged in clusters with a triangular shape, the pinnately divided leaf clusters of the poison hemlock are remarkably large — they can be as long as 20inches (50 centimeters) and 16 inches (40centimeters) wide. Succinctly said, the leaf clusters look like ferns.
- The color of Conium maculatum‘s singular stem, from which multiple branches protrude at roughly a 45 degree angle, can vary quite widely. The stem may have a copper-brown, green, burgundy, or even deep purple shade. The distinctive feature, which can also be used to tell poison hemlock apart from similar-looking plants, is that poison hemlock has completely smooth and hairless stems.
- Poison hemlock produces deceptively showy flowers, which have five petals each. These flowers grow at the end of long stalks in large clusters, forming umbels. Each cluster of flowers will also have some brown bracts below it. Poison hemlock flowers during the summer.
- After the flowers recede, poison hemlock produces tiny seeds, which are easily carried by the wind, causing the plant to proliferate.
- You can typically find Conium maculatum in areas with lots of water — around ponds, in woodlands, and near streams, for instance. They quickly take over any uncultivated area, however, and are also often seen along roads or in ditches. If you’re not careful, poison hemlock may soon find its way to your garden, too.
What Are the Symptoms of Hemlock Poisoning?
Every single part of Conium maculatum is poisonous — that means the bark, stem, leaves, flowers, seeds, fruits (which cover the seeds when first released), roots, and the sap.
Poison hemlock is not only poisonous to people, but also to every other mammalian species. Your pets and farm animals, whether cats, horses, dogs, sheep, cows, or goats can all die as a result of ingesting poison hemlock — and so can you or your children.
The toxicity of poison hemlock does vary through its growth cycle, and the symptoms and severity of hemlock poisoning depend on this as well as the quantity that was ingested. The first symptoms can set in anywhere from half an hour to several hours after eating any part of the plant, and they include:
- Trembling or shaking
- Increased salivation
- Nausea and vomiting
- Diarrhea, sometimes with visible bleeding
- Extreme discomfort of the digestive tract, most often described as a burning feeling
- Muscle weakness and even paralysis
- Dilated pupils
- Initially, a racing heart — and later, a worrying slowing of the heart rate and a weak pulse
- Losing the ability to speak
- Trouble breathing due to paralysis of the respiratory tract
- In livestock, skeletal birth defects have been reported after an animal ingests poison hemlock during pregnancy
As if all that didn’t sound scary enough already, there’s another important thing to be aware of before you think that this poisonous plant, too, deserves a little love, and you’d actually love to keep this beautiful “underdog” around in your garden. There’s no antidote to hemlock poisoning.
That means that people and animals who are dealing with hemlock poisoning can only be offered supportive care. Each of the symptoms will be treated individually — and patients will be offered fluids to support their recovery. Medical professionals, whether doctors or veterinarians (depending on the victim) can try to speed up the removal of the poison, but cannot offer a definitive cure.
You know what that means — where there is no cure, prevention becomes the cure. If you have Conium maculatum in your garden, you are living with a ticking time bomb. You need to eliminate it. If you are, by any chance, a fan of the modern foraging movement that has recently become popular, you need to be very well-versed in plant identification. Poison hemlock certainly isn’t the only plant or fungus you could mistake for a tasty snack.
Do note that poison hemlock is actually not among the plants that will cause contact dermatitis, so touching it shouldn’t immediately cause you to panic. All the problems associated with poison hemlock occur after eating it, but even small amounts can be extremely hazardous. Despite that fact, you are warmly recommended to don gloves, face masks, and other protective gear before interacting with poison hemlock.
What Not to Do With Poison Hemlock
If you have spotted poison hemlock in or near your garden, you may be tempted to simply mow the plant down.
Not only does this come with the obvious disadvantage that you would be leaving the plant’s strong and sturdy root system in place (meaning that poison hemlock will definitely come back to haunt you), but you’d also risk:
- Spraying the extremely poisonous sap (which can also release toxic fumes) all over your garden, and perhaps into your face.
- Spreading the seeds of Conium maculatum far and wide, causing the flowering plants to appear in numerous new locations. In other words, multiplying the problem.
Cutting the stems down poses a similar problem, and is therefore not recommended either.
Burning the plant down is another non-recommended strategy to its elimination, because the fumes resulting can irritate the airways severely, especially in sensitive groups.
How to Get Rid of Poison Hemlock
Four viable approaches to eliminating poison hemlock, a highly invasive plant, exist. They are manual, mechanical, chemical, and biological.
Manually Removing Poison Hemlock From Your Garden
To manually remove poison hemlock, you are advised to don personal protective equipment and to ensure that vulnerable people and animals are nowhere near the site. Dig around the location of the plant to safely remove it by its roots, taking care not to leave any part of the roots in place. Once removed from the soil, place the poison hemlock in a plastic garbage bag, even using several layers of bags. Do not compost these plants as they will return with a vengeance.
Mechanical Ways to Control Poison Hemlock
Your average gardener should not necessarily attempt this, but some people choose to mow Conium maculatum with a weed eater before their growing season starts, and before they start flowering or producing seeds. This will leave the root systems in place. That is why this kind of removal must immediately be followed up by mulching, the planting of other prolific (but non-poisonous) plants who can quickly take over the area, or both. This may be done in wastelands, and not in gardens where people often spend time.
Using Herbicides to Kill Poison Hemlock
Herbicides are an effective approach when used in the early spring. Typically, Weedmaster and Milestone are recommended. These herbicides should applied to the entire plant’s surface, while the gardener is wearing personal protective equipment (including long sleeves). It may have to be repeated several times.
Biological Control: Poison Hemlock Moths
The larvae of these moths only feed on poison hemlock, and can be a relatively effective way to control the plant’s growth.
Do all of those options sound equally intimidating to you, and are you 100 percent sure you have poison hemlock in your garden? Calling a landscaping company that is confident about their ability to manage highly poisonous plants is a great solution to your problem.
► Chemical There are two herbicides that can be used to control Poison hemlock they are both non-selective chemicals and kill nearly all types of plants. Glyphosate is a non-selective active ingredient found in a number of products (like RoundUp Pro® , with 41% glyphosate) that are effective in controlling hemlock.Should you get rid of hemlock? ›
To prevent hemlock poisoning, the best thing you can do is eliminate the plant. To get rid of poison hemlock, dig it out in small patches. Make sure to remove the roots. You can use herbicide on the plants in late fall or early spring, but not after their flowers have bloomed.When can I remove poison hemlock? ›
Timing. Controlling poison hemlock is best accomplished in the winter and early spring when the plant is still in the rosette stage (all growth low to the ground). Once the plants start to form flowering stalks, they become more difficult to kill.How does poison hemlock look like? ›
Look for small clusters of white flowers that eventually develop into “green, deeply ridged fruit that contains several seeds,” USDA states. “After maturity, the fruit turns grayish brown.”Can poison hemlock be absorbed through the skin? ›
The toxins can also be absorbed through the skin and lungs, so be sure to wear gloves and a mask when handling these plants.What happens if you breathe in poison hemlock? ›
All parts of this plant contain toxic alkaloids that can be fatal even in small amounts. The alkaloids can affect nerve impulse transmission to your muscles, eventually killing you through respiratory failure.Can I mow poison hemlock? ›
Mechanical: Caution: toxins can be inhaled when mowing poison hemlock. Mowing is not recommended due to risk of breathing in toxins. In addition, cut plants can regrow.How do I stop my hemlock from growing? ›
Plowing or repeated cultivation of newly germinated plants will prevent poison hemlock establishment. In areas where cultivation isn't practical or possible, repeated mowing once the plants have bolted but before they have flowered can reduce further seed production.How did poison hemlock get in my yard? ›
Generally speaking, the most common ways to end up with a poison hemlock garden problem include: Seeds spreading from bird droppings. Mice or other garden pests carrying the seeds into the garden. Contamination of purchased garden soil.Should you burn poison hemlock? ›
Do not burn the plant, as the smoke can contain deadly toxins. In fact, hemlock is so poisonous that some of poison hemlock's alkaloid compounds have the ability to pass into milk when animals feed on sublethal amounts of this plant, which can adversely alter the flavor and safety of milk used for human consumption.
It's also very toxic for humans. Simply touching the plant can make you sick.” Poison hemlock features white, umbrella shaped flower clusters with fern-like leaves.What to do if you find hemlock? ›
If you find poison hemlock in your yard, remove it quickly to keep it from spreading. Wear gloves and pull up the entire plant, including the roots. Your local Office of Agriculture might be willing to help you remove poison hemlock.What does poison hemlock look like in the fall? ›
Plants emerge as a cluster of leaves that form a rosette. Poison hemlock is most noticeable at this stage of growth in late fall through early spring with its parsley-like leaves which are highly dissected or fern-like. The individual leaves are shiny green and triangular in appearance.What to do after touching poison hemlock? ›
Though Healthline states that there is no known antidote to hemlock poisoning, if you think you may have touched any part of the plant, breathed in its particles, or been otherwise exposed, you should seek medical attention immediately.What part of the body does hemlock affect? ›
The general symptoms of hemlock poisoning are effects on nervous system (stimulation followed by paralysis of motor nerve endings and CNS stimulation and later depression), vomiting, trembling, problems in movement, slow and weak later rapid pulse, rapid respiration, salivation, urination, nausea, convulsions, coma and ...What is the difference between hemlock and poison hemlock? ›
Water hemlock has a spotted stem like poison hemlock, but is a perennial that produces a cluster of fleshy tubers at crown, and the leaflets are not finely divided like poison hemlock. Miscellaneous: Poison hemlock contains the toxin coniine which disrupts the central nervous system.Is hemlock poisonous to dogs? ›
Is Poison Hemlock Toxic to Dogs? Poison hemlock is toxic, when ingested, to people, livestock and, yes, cats and dogs. However, only livestock, who may get it mixed up with hay or eat it in large amounts in a field, are likely to eat enough to cause severe poisoning, Schmid says.How deep do hemlock roots go? ›
Under ideal growing conditions, seedlings of eastern hemlock develop slowly. First-year seedlings may grow only 25 to 38 mm (1 to 1.5 in) in height and the roots extend less than 13 mm (0.5 in) into the soil. These conditions provide moisture in the upper soil horizon throughout the growing season.What kills hemlock trees? ›
The hemlock woolly adelgid feeds on the sap at the base of hemlock needles, disrupting nutrient flow and causing the needles to change from deep green to a grayish green, then fall off. Without needles the tree starves to death, usually within three to five years of the initial attack.How long does hemlock last in the ground? ›
Hemlock is locally widely used for raised garden beds, fencing, and barn construction and repair. There is no guarantee as to how long the wood will last in the ground, but in the right conditions, some people report that it lasts 5 to 7 years.
Lifecycle: Poison hemlock germinates from seed and is a biennial plant with a basal rosette of leaves during its first year. Once it overwinters, in late April/early May, it bolts into an erect branched plant producing prominent white flowers in an umbel generally in June and July.How quickly does poison hemlock take effect? ›
Ingestion of the hemlock plant can take 30 minutes to a few hours to give rise to the poisoning symptoms. The severity of the symptoms depends on how long the plant is there in your system. The common signs and symptoms include: Shivering (tremors)Is poison hemlock worse than poison ivy? ›
Poison hemlock has more severe toxic properties than poison ivy and is quickly growing throughout the area. The flowers are tiny, white and arranged in small, umbrella-shaped clusters.What part of hemlock is most poisonous? ›
All parts of the plant are toxic, especially the seeds and roots, and especially when ingested.What happens if I touch my hemlock? ›
If You've Touched This Plant, Call Your Doctor Immediately, Experts Warn. It looks harmless, but can be deadly—and it almost killed an Ohio man. Spring brings warmer weather, sunny skies, and plants bursting into bloom all over—but you might want to exercise caution when stopping to smell the roses this year.Can you survive poison hemlock? ›
In humans, coniine affects the nervous system and causes tremors, paralysis, and breathing difficulties. Muscle damage and kidney failure may occur in severe cases. A person with poison hemlock toxicity can usually be successfully treated in a hospital.Can you get sick just by touching poison hemlock? ›
It's also very toxic for humans. Simply touching the plant can make you sick.” Poison hemlock features white, umbrella shaped flower clusters with fern-like leaves.What will hemlock do to a person? ›
The general symptoms of hemlock poisoning are effects on nervous system (stimulation followed by paralysis of motor nerve endings and CNS stimulation and later depression), vomiting, trembling, problems in movement, slow and weak later rapid pulse, rapid respiration, salivation, urination, nausea, convulsions, coma and ...How does poison hemlock get in your yard? ›
Generally speaking, the most common ways to end up with a poison hemlock garden problem include: Seeds spreading from bird droppings. Mice or other garden pests carrying the seeds into the garden. Contamination of purchased garden soil.