When out foraging for edible and medicinal plants, it is just as important—if not more so—to know how to identify the poisonous plants that grow in your region. Poison hemlock (Conium maculatum) is one of those that everyone should know how to identify, as it can be quite prolific in some areas.
If you want to learn more about the edible and medicinal weeds that surround us and how to use them, check out my eBook: Wildcrafting Weeds: 20 Easy to Forage Edible and Medicinal Plants (that might be growing in your backyard)!
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About Poison Hemlock
Poison hemlock (Conium maculatum) is in the Apiaceae family, which also includes carrots, parsnips, parsley, fennel, and their wild counterparts.
It is an herbaceous biennial plant that can grow 5 to 10 feet (2-3 meters) tall or even taller.
It should not be confused with hemlock the coniferous tree whichis completely harmless (and edible).
All parts of the plant are poisonous, including the flowers, leaves, stems, roots, and seeds.
Poison hemlock contains potent toxic alkaloids that affect the nervous system, and even small internal doses can cause respiratory collapse and death.
It can also cause a severe skin reaction similar to a burn when touched externally. Definitely not a plant to mess around with!
Historically poison hemlock was used in ancient Greece to poison condemned prisoners, and it was what killed Socrates after he drank a potent hemlock infusion.
First: Get a Foraging Guidebook
To the untrained eye poison hemlock can sometimes be confused for some popular foraging plants such as Queen Anne’s lace, yarrow, wild fennel, and elderflower.
Before doing any foraging or wildcrafting, especially for plants that may resemble poison hemlock, it’s extremely important to get a foraging guidebook. Here are a few of my favorites:
- The Forager’s Harvest by Samuel Thayer
- Nature’s Garden by Samuel Thayer
- Identifying and Harvesting Edible and Medicinal Plants by Steve Brill
Related: 12 Best Books on Foraging and Wildcrafting
Where Does Poison Hemlock Grow?
Poison hemlock (Conium maculatum) is native to Europe and North Africa, but has widely naturalized in many other areas. It is found in almost every state in the United States, and in most Canadian provinces.
I didn’t find any distribution maps for other countries, but poison hemlock does also grow in Europe, North Africa, Asia, Australia, and New Zealand.
Poison hemlock naturalizes very easily and can be found growing in disturbed areas, along roadsides and trails, and in damp areas along streams.
In our region I find it alongside bike paths, near park edges and fields, and in dense colonies near the freeway.
If you happen to find poison hemlock in or near your yard it is advised to properly remove it as soon as possible, especially if there are children around.
How to Identify Poison Hemlock
Poison hemlock really isn’t hard to identify, and there are a few key identification features to be on the lookout for.
The most important identification feature of poison hemlock are the stems and stalks.
Poison hemlock stems are hairless, hollow, and almost always have distinctive purplish-red splotching or streaking on them, especially towards the base of the plant.
These purple or reddish colored markings are a sure giveaway that it is poison hemlock.
Many sources say that the stems of poison hemlock don’t always have this splotching, though I have never found poison hemlock without it.
Regardless, it’s always a good idea to know more than one identification feature, especially when dealing with poisonous plants.
Poison hemlock flowers can be confusing because they resemble other white umbel shaped flowers, especially those in the Apiaceae family.
The flowers bloom in late spring and grow in rounded clusters that are called compound umbels. Each individual tiny flower has five petals.
After the flowers bloom they form small green fruits with wavy ribs that contain highly poisonous seeds that resemble anise, fennel, or caraway seeds.
Poison hemlock flowers grow on highly branched stalks that can grow up to 8-10 feet (3 meters) tall.
The leaves of poison hemlock look very similar to parsley, chervil, and wild carrot (Queen Anne’s lace), which makes them difficult to distinguish.
They are opposite and compound, hairless, lacy, and triangular in shape.
When crushed or brushed against, the leaves emit a very unpleasant musty smell, not at all carrot-like like Queen Anne’s lace.
Potential Poison Hemlock Look-Alikes
The reason it’s so important to learn how to identify poison hemlock (Conium maculatum) is because it is often mistaken for other plants that are edible and medicinal, most notably Queen Anne’s lace.
Here I will explain the major differences between the edible and medicinal plants that poison hemlock can potentially look similar to.
Queen Anne’s lace (Daucus carota)
There are several differences here to consider.
First is overall size, as Queen Anne’s lace only grows to about 2-3 feet in size.
Queen Anne’s lace has hairy stems and leaves, while poison hemlock’s are smooth. Here is one easy way to remember it: “the Queen has hairy legs.”
Queen Anne’s lace flowers bloom later in the summer and have a flatter shape. They typically have a single dark purple or red flower in the center.
Queen Anne’s lace also has 3 pronged bracts at the base of the flowers, and the older flowers curl up into a bird’s nest shape.
Queen Anne’s lace flowers
Yarrow (Achillea millefolium)
The biggest difference that yarrow has from poison hemlock is its distinctive frilly, feather-like leaves. You can see pictures of the leaves in my post about foraging yarrow.
The flowers also look a bit different, as yarrow is not in the Apiaceae family so does not have a true umbel flower.
Yarrow is also a smaller plant, growing to about 2-3 feet in size.
Angelica (Angelica spp.)
Angelica has similar looking flowers to poison hemlock, although even more rounded and sometimes light green in color.
The leaves of angelica are much larger and are compound with dozens of leaflets. There is also a sheathing base where the leaf meets the stem.
Perhaps the most noticeable feature of angelica is its pleasantly fragrant scent.
Angelica can also look very similar to water hemlock (Cicuta spp.), which is another highly poisonous species that can cause death.
Cow Parsnip (Heracleum maximum)
The flowers of cow parsnip are similar to poison hemlock, but much larger, and same goes for the leaves.
It can also closely resemble water hemlock, so be absolutely certain of your identification.
Cow Parsley/Wild Chervil (Anthriscus sylvestris)
Cow parsley has pink stems that are slightly hairy and have a groove.
Be aware that it can also closely resemble fool’s parsley, another poisonous plant.
Wild Parsnip (Pastinaca sativa)
Wild parsnip has yellow flowers and the stem is grooved.
Be aware that while this plant has edible roots, the leaves and stems can cause burns and blisters on the skin after touching.
Water Parsnip (Sium suave and Berula spp.)
Water parsnip grows in marshes and wet areas, and the leaves are not lacy like poison hemlock.
I highly recommend using the book Incredible Wild Edibles by Samual Thayer for identifying this species.
Water parsnip looks very similar to water hemlock, another deadly plant, so great care should be taken to obtain positive identification before harvesting.
Wild Fennel (Foeniculum vulgare)
Wild fennel has a similar overall structure to poison hemlock.
The main differences is that wild fennel has yellow flowers, frond like leaves, and smells strongly of fennel or anise (a licorice-like scent).
Elderflower (Sambucus spp.)
There is only one minor similarity thatelderflowers might have to poison hemlock, and that is the white flowers.
Elderflowers do not have the true umbel shape and are usually much larger. They turn into elderberries as the summer progresses into fall.
The elder plant itself is more of a large tree-like shrub and doesn’t really bear any resemblance to poison hemlock.
Three Other Similar Looking Poisonous Plants
It’s also worth mentioning that there are three other poisonous plants that are also in the Apiaceae family that look somewhat similar to poison hemlock and the other plants I listed above.
- Water Hemlock (Cicuta spp.) – water hemlock is more deadly than poison hemlock and is almost as widespread. There are four different varieties, with spotted water hemlock (Cicuta maculata) being the most common.
- Giant Hogweed (Heracleum mantegazzianum)– giant hogweedis literally giant, growing up to 18 feet (6 meters) in height with leaves that are 3-5 feet (1-2 meters) wide and flowers that can be 2.5 feet (almost 1 meter) in diameter. It causes horrible skin blistering, permanent scars, and blindness.
- Fool’s Parsley (Aethusa cynapium) – fool’s parsley is less poisonous than poison hemlock, but is still one that you most definitely want to avoid. It has hairless stems and long bracts that hang below the secondary flower clusters.
Apiaceae can be a tricky family to identify, especially when there are several poisonous species to worry about. Poison hemlock really isn’t hard to identify once you know what to look for.
This guide is here help you learn all of the features of poison hemlock and its look-alikes so that you can feel more confident in your foraging adventures!
A tall, upright plant, hemlock can be distinguished by the distinctive and unpleasant, mousy smell of its foliage and its purple-spotted stems. Its leaves are finely divided and large, and its flowers are small and white and appear in umbrella-like clusters.
Poison-hemlock stems have reddish or purple spots and streaks, are not hairy, and are hollow. Leaves are bright green, fern-like, finely divided, toothed on edges and have a strong musty odor when crushed. Flowers are tiny, white and arranged in small, umbrella-shaped clusters on ends of branched stems.
The flowers bloom in late spring and grow in rounded clusters that are called compound umbels. Each individual tiny flower has five petals. After the flowers bloom they form small green fruits with wavy ribs that contain highly poisonous seeds that resemble anise, fennel, or caraway seeds.
Poison hemlock stems are smooth, while Queen Anne's Lace stems are covered with tiny hairs. Poison hemlock also has dark purplish splotches on its stem, whereas Queen Anne's Lace has a solid green stem.
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.
Eastern hemlock bark is cinnamon-red to gray and is divided into narrow, rounded ridges, which are covered with thick scales. As the bark matures, it becomes scaly and deeply fissured.
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.
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. Even touching this plant may cause a skin reaction in some people. To date, there is no antidote.
Water hemlock has small, white flowers that grow in umbrella like clusters. Side veins of the leaves lead to notches, not to tips at the outer margin. The thick rootstalk of water hemlock contains a number of small chambers.
Here's how to spot the differences
Poison hemlock displays multiple flowers, while Queen Anne's lace has one. Queen Anne's lace has a hairy stem, and poison hemlock's stem is smooth. Queen Anne's lace has a tiny purple flower in its center, and poison hemlock does not.
Though the two plants have similar leaves, there are definite differences in their leaf structure. Yarrow's leaves are frilly, thin, and fern-like. Hemlock's leaves are broader across the middle, flatter, and have a similar shape to those of parsley. Yarrow on the left, hemlock on the right.
The stems of both poison-hemlock and Queen Anne's lace are hollow, but poison-hemlock will have small purple spots all over its smooth stem, according to the USDA. Queen Anne's lace has no purple spots and is hairy, according to U.S. Fish and Wildlife Service.
All parts of the plant are toxic, especially the seeds and roots, and especially when ingested.
► 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.
The toxins can also be absorbed through the skin and lungs, so be sure to wear gloves and a mask when handling these plants.
Poison hemlock plants form rosettes that remain green throughout the winter in a somewhat semi-dormant stage (Figure 1). These young rosettes are often found in areas where poison hemlock was present the previous year, particularly along fence rows and other isolated areas.
Small stands of poison hemlock can be controlled through hand removal. Plants should be dug, taking care to remove the entire long taproot. Plant parts should be disposed of responsibly, as plant parts remain poisonous even after dried.
There are various herbicides that may help with preventing and managing poison hemlock. Spraying the foliage in spring and once more in late sum- mer has proven to be effective in management of this weed. Spraying may prevent regrowth but not seed production in mature plants, making re-spray paramount.
The heartwood of eastern hemlock is pale brown with a reddish hue. The sapwood is not distinctly different in coloration, but may appear lighter. The wood is coarse and uneven in texture.
The soil organic horizon under mature stands ranges from less than 7 to more than 57 cm (2.8 to 22.5 in); the average depth increases from 11.4 cm (4.5 in) on soils with good drainage to 43.2 cm (17.0 in) on poorly drained soils.
Hemlock trees have needles uniquely attached to the stem. It is similar to the stalk-like woody projections of a spruce but much finer. Photo by Matt Suwak. Also, the needles of a hemlock are flattened.
Poisoning. Hemlock is highly toxic to livestock and humans and can be fatal. Both the growing and cut dried plant are poisonous. Those with hemlock poisoning will display symptoms after 30 minutes to three hours depending on the amount ingested.
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 ...
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.
Major toxicity and death occur when a depression phase develops. The heart and the diaphragm muscles can slow down more and more, causing death. In humans, coniine affects the nervous system and causes tremors, paralysis, and breathing difficulties. Muscle damage and kidney failure may occur in severe cases.
The plant can be found in every state in the country, with the exception of Alaska, Florida, Hawaii and Mississippi, according to the USDA.
Poison hemlock (Conium maculatum) is a plant that is poisonous for humans and animals. Accidental ingestion of the plant may result in central nervous system depression, respiratory failure, acute rhabdomyolysis, acute renal failure and even death.
Water hemlock is UNSAFE for anyone to take by mouth or apply to the skin. All plant parts are poisonous and can cause death in as little as 15 minutes. Even applying water hemlock to your skin can cause death. Get immediate medical attention if you have taken water hemlock.
Chemical screening test for alkaloids in plant material provides confirmation of toxicity due to poison or water hemlock. However, a plant specimen (or ingested material) is required, and these tests are not routinely available.
The alkaloids slowly poison the nerve-muscle junctions and cause the failure of the breathing muscles. Even touching this plant may cause a skin reaction known as dermatitis (itchy skin rash) in sensitive people. Lack of antidote makes hemlock poisoning more difficult to treat.
Closely related to poison hemlock (the plant that famously killed Socrates), water hemlock has been deemed "the most violently toxic plant in North America." A large wildflower in the carrot family, water hemlock resembles Queen Anne's lace and is sometimes confused with edible parsnips or celery.
Cow parsley has U shaped leaf stems (or more like a D on its side). Hemlock has rounded leaf stems, though these do form sheaths near their base. Cow parsley leaf stems and flowering stems tend to be greenish – purple, sometimes entirely purple, but they are NEVER blotchy.
Furthermore, to some individuals, elderberry plants look like a few different plants, some of which are extremely poisonous. To the untrained eye, elderberry can often be confused with pokeberry or even poison hemlock. What separates elderberry from some other look- alikes is bark.
Like other members in this plant family, poison hemlock flowers have white, umbrella-shaped clusters in addition to the fernlike appearance of the leaves. This why people over the years have mistaken poison hemlock for wild carrot, wild parsnip, or wild parsley.
Poison hemlock, which resembles Queen Anne's Lace, can be spotted in highway right-of-ways, along fences and on the edges of farm fields. In just the last year, however, the plant that was originally brought to the U.S. from Europe has migrated near more populated areas, which has experts concerned.
People are usually poisoned when they eat hemlock mistaken for plants such as parsley, wild carrot or wild anise. Although, cattle seldom eat hemlock, they will if no other forage is available or if it is incorporated in hay or silage.
The term sardonic grin comes from the grisley practice in Phoenician Sardinia of disposing of criminals and old people using Hemlock Water Dropwort. The poison acts by constricting the muscles causing death by asphixia which also causes a rictus like death grin, the sardonic grin.
Goats and sheep can eat as little as 3 ounces of the plant and show clinical signs; however sheep tend to be able to metabolize the toxin better than most species. The toxin also causes birth defects in goats. If an animal does not progress to respiratory distress and death, prognosis is good for recovery.
Plant parts will remain poisonous for several years. As far as Philip's question, poison hemlock will not affect your garden plants or soil. However, care must be taken to avoid confusing poison hemlock with other related plants, such as parsnip, parsley, and Queen Ann's lace.
Poison hemlock isn't like poison ivy, poison oak or poison sumac. You usually won't get a rash from touching it. Most of the time, hemlock is only poisonous if ingested.
Look at the roots. Osha roots have a brown hairy fringe around the top of the dark root. Look at the stem. If it had purple spots or stripes, it is poisonous hemlock.
For a person who wants to buy hemlock for construction,&bsp; sawn, air dried rough hemlock lumber sells for $. 90 a board foot($900/thousand bd. ft.). Kiln dried lumber will bring $1.00 board foot and planed lumber will add another 10 cents per board foot.
The toxins can also be absorbed through the skin and lungs, so be sure to wear gloves and a mask when handling these plants.
An herbicide containing a 41% or higher concentration of glyphosate should be used, and it should be mixed to a 2% product spray solution. Glyphosate will kill grass and other vegetation so care should be taken if used around desired vegetation.