The poison hemlock (Conium maculatum L.) is a dangerous plant that grows throughout the United States. The hemlock plant has white flowers that grow in clusters, and the stem has purple spots. This plant can grow up to 9 feet tall.

It was initially brought over from Europe as a garden plant. Hemlock typically grows in the spring, but in some locations it can grow as year-round.

Hemlock poisoning occurs after ingesting any part of the plant, such as the seeds, flowers, leaves, or fruits. 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.

The leaves are particularly poisonous in the spring, up until it produces flowers. The roots of poison hemlock can easily be mistaken for wild parsnips, while the leaves can be mistaken for parsley. This is the primary culprit for accidental poisoning.

Poison hemlock is often found on roadsides, in waste areas and near fences. It can be mixed in with harmless plants in pastures and crops, making this plant particularly dangerous to livestock. However, its unpleasant, musty odor usually causes animals to avoid it unless there is no other foliage or feed available to eat.

Poison hemlock is also known as:

  • deadly hemlock
  • poison parsley
  • California fern
  • spotted hemlock
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All parts of the poison hemlock plant, including leaves, stem, fruit, and root, are poisonous to humans and livestock. Image source: iStockphoto

Symptoms of hemlock poisoning can appear anywhere between 30 minutes to hours after ingesting the plant. The severity of your symptoms greatly depends on how much of the plant is in your system and the toxicity of the plant at its time of growth.

Common symptoms of hemlock poisoning may include:

In more severe cases, ingesting this plant can cause serious health issues. Complications from hemlock poisoning include:

If you begin to experience any adverse reactions after touching, tasting, or eating a poison hemlock plant, seek immediate medical attention.

To date, there is no antidote for hemlock poisoning. Treatment depends on the severity of your condition and your symptoms.

If you’re having difficulty breathing, your doctor will look for ways to secure your airway and may assist with ventilation. Your doctor will also try to decontaminate your gastrointestinal tract in order to remove the hemlock from your system.

If you begin to experience seizures, you may be treated with antiseizure medication to lessen symptoms. You may also be treated with fluids intravenously to prevent dehydration and restore nutrient levels.

Removing this plant is the primary method of prevention. Experts recommend digging out small patches to remove them, being sure to remove the root. Cutting or mowing hemlock plants can cause them to resprout and emit toxic fumes if they’ve already matured.

Don’t burn these plants. The fumes can trigger asthma symptoms and increase your risk of developing a reaction.

You can also use herbicides to kill hemlock plants, but they are useless after hemlocks have sprouted flowers. The best time to use herbicides is in the late fall or early spring, right as the plants begin to grow.

Before interacting with poison hemlock plants, wear gloves, face masks, and other protective clothing to prevent an adverse reaction. After removing hemlock, place the plants in a plastic bag before throwing them in the trash to avoid further contamination.

Hemlock poisoning can be fatal, and there is no antidote. Symptoms can begin showing as early as 30 minutes after ingesting the plant. The severity of your poisoning depends on how much hemlock is in your system and how toxic the plant was at the time of ingestion.

Use caution when touching or experimenting with new plants. If you’re foraging, pay special attention to plants that look like wild carrots, parsnips, parsley, and other vegetables and herbs to ensure it’s not hemlock.

If you begin experiencing irregular symptoms after eating a plant or herb, seek immediate medical attention.