These sources of poison could be in your backyard

By Alistair Gardiner
Published August 13, 2021

Key Takeaways

Do you think poisonings are the stuff of medieval folklore? Think again. According to the University of Missouri, roughly 2 million cases of accidental poisoning are reported to poison control centers across the country every year—that’s about one every 15 seconds. And, believe it or not, 3% of these are due to the consumption of toxic plants.

There are an estimated 500 species of poisonous plants growing in the United States, and while some of these, like poison ivy, are easily recognizable by most people, many others are inconspicuous. With summer upon us, most of us are spending more time outdoors. So, to help you and your family stay better protected, here are five common, dangerous, wild-growing plants to look out for when strolling in nature—or even just your own backyard.


The oleander plant (Nerium oleander), with its gorgeous pink or white blossoms, may look friendly—but don’t let its appearance deceive you. According to the Colorado State University (CSU) poisonous plants database, consuming a single leaf of this plant can be lethal for a child. 

Oleander, also known as the rose laurel, is found throughout the country, primarily in states that have a milder winter, and has grown in popularity as a potted house plant. Unfortunately, this perennial, evergreen shrub contains oleandrin and nerine, which are potent cardiac glycosides (cardenolides). Eating any part of an oleander can cause vomiting, difficulty breathing, impaired vision, and cardiac arrhythmias. 

While mortality events are rare in humans, consuming the plant can cause sudden death in acute cases. This is due to the cardiac glycosides, which inhibit the cellular membrane sodium-potassium pump, which leads to a drop in intracellular potassium and a spike in serum potassium. The result is a decline in electrical conductivity through the heart, followed by irregular heartbeats, and eventually a full halt to all cardiac activity.

Water hemlock  

Water hemlock (Cicuta sp.) looks very similar to the benign plant cow parsley, but beware—according to the USDA Agricultural Research Service, water hemlock is “the most violently toxic plant that grows in North America.”

Water hemlock is a perennial with small white flowers that grow in clusters. It is usually found in wet areas of meadows and pastures, and around streams. It typically begins growing in the spring and flowers in June or July, in higher elevations.

The toxic ingredient in water hemlock is cicutoxin, an unsaturated alcohol with a strong carrot-like odor. This poisonous substance is mainly found in the plant’s tubers, but is also present in the leaves, stems, and seed heads. According to the USDA, just a small amount of cicutoxin is required to poison an animal or a human. 

Cicutoxin acts directly on the central nervous system and results in violent convulsions. Other signs of poisoning include nervousness, excessive salivation and frothing, muscle twitching, rapid pulse, and tremors. In acute cases, poisoning can lead to a coma or death in as little as 15 minutes. 

Deadly nightshade 

Perhaps the most famous (or infamous) plant on this list, deadly nightshade (Atropa belladonna) 

grows in well-drained sandy loams, and can be found in various states, including New York, Michigan, California, Oregon, and Washington.

According to the Missouri Botanical Garden, the plant’s leaves, berries, and roots are extremely toxic because they contain tropane alkaloids. These include atropine, scopolamine, and hyoscyamine. In small doses, consuming the plant can cause delirium and hallucinations in humans; larger doses can be fatal. When the berries are green before ripening, they are toxic. As few as two berries can kill a child, while 10 berries on average can be fatal for an adult.

Other signs of poisoning include tremors, diarrhea, slow heart rate, labored breathing, kidney failure, drowsiness, and depression.


Jimsonweed (Datura stramonium) is another member of the nightshade family. While less famous than its cousin, this plant, also known as thorn apple, contains a set of very similar toxic substances, including a series of alkaloids, the most toxic of which are hyoscyamine, hyoscine (scopolamine), and atropine.

These substances act on the autonomic nervous system, and the results of poisoning include impaired vision, extreme thirst, decreased gastrointestinal activity, increased heart rate, and convulsions, according to CSU’s database. Most cases of human poisoning happen when individuals eat the seeds of the plant in order to experience hallucinogenic effects.

Death camas

There are 15 different species of death camas (Zigadenus spp) that grow across the United States in a variety of habitats, from sandy hills and plains to wet mountain valleys. The bulbs and leaves of this perennial are its most toxic parts, due to the presence of several steroidal alkaloids, which have potent hypotensive activity. 

When consumed by humans, symptoms of poisoning include vomiting, muscular weakness, tremors, ataxia, convulsions, coma, and death.

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