According to the Arizona Native Plant Society, Arizona is home to 4,000 native plants and approximately 300 of them are poisonous and could harm people and pets. Some of these plants can be toxic by ingesting or even touching them.
Oleander — a widely used landscape plant — is highly poisonous if ingested, causing severe stomach pain, vomiting and even heart problems. Another dangerous plant is jimsonweed, which can cause hallucinations, seizures and respiratory failure if consumed. Contact with Arizona poison ivy can result in skin irritation and intensely annoying rashes.
Here's everything you need to know about toxic and poisonous plants in Arizona, including symptoms of exposure and steps to take if you or your pet come into contact with these hazardous plants.
Are there any poisonous plants in Arizona?
Yes, Arizona is home to hundreds of poisonous plants that can pose risks to humans and animals if eaten or touched.
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“The Sonoran Desert is actually known for being very rich in chemical diversity," said Julie Stromberg, an associate professor emeritus in the School of Life Sciences at Arizona State University.
"Some of those chemicals are used medicinally, some are toxic, some have to defend the plant from being eaten, some plants protect themselves with spines and thorns, and some of those chemicals are toxic to humans as well as to other creatures.”
Matt Chew, faculty associate at the School of Life Sciences at ASU, described some of the most notable poisonous plants in Arizona:
- Jimsonweed: This plant contains toxic alkaloids that can cause hallucinations, rapid heart rate, dry mouth, blurred vision and even coma or death if ingested in large quantities. You can find jimsonweed on well-drained, sandy soils or roadsides.
- Poison ivy: Contact with poison ivy can cause a rash, itching, redness and blistering due to the plant's urushiol oil. It's common near water and around rich soil in ravines and canyons.
- Water hemlock: Water hemlock is one of the most toxic plants in North America, containing the deadly toxin cicutoxin. Ingesting even small amounts of water hemlock can lead to seizures, respiratory failure and death. You can find it in moist soils along the edges of standing or running water, in shady locations or on roadsides at elevations of 4,500 to 10,000 feet.
- Death camas: All parts of the death camas plant contain toxic alkaloids that can cause nausea, vomiting, diarrhea, convulsions and coma if ingested. Can be found in meadows, grasslands and open woodlands.
- Desert rose: Desert rose contains cardiac glycosides, which can cause nausea, vomiting, abdominal pain, irregular heart rate and cardiac arrest if ingested. Typically found in gardens and is popular as a potted plant indoors or on patios.
- Morning glory: The seeds of some morning glory species contain lysergic acid, a compound that can cause hallucinations, nausea, vomiting, diarrhea and dizziness if ingested in large quantities. The plant itself is generally not harmful, but the seeds pose a risk if consumed. You might encounter morning glory vines climbing fences or other structures.
- Milkweed: Ingestion of milkweed can cause nausea, vomiting, diarrhea, seizures and respiratory paralysis due to toxic glycosides, specifically cardenolides. While essential for monarch butterflies, milkweed is poisonous to livestock and pets. Can be found in open fields and along roadsides.
- Castor bean: The castor bean plant contains ricin, a highly potent toxin. Ingestion of even a small amount can lead to severe abdominal pain, vomiting, diarrhea and potentially fatal organ failure. Ricin is one of the most toxic naturally occurring substances. Can be found in vacant lots or in warmer and more arid areas.
- Tomato plants: The tomato fruit is safe and widely consumed. Other parts of the plant, including the leaves and stems, contain toxic compounds known as glycoalkaloids, specifically tomatine and solanine. Ingesting tomato leaves and stems can cause nausea, vomiting and dizziness, though large amounts would need to be consumed to cause serious harm.
- Desert tobacco: It contains nicotine and other alkaloids that are toxic to humans and animals if ingested. Symptoms include nausea, vomiting, diarrhea, abdominal pain, increased heart rate, respiratory distress and even death in high doses. Can be found in sandy areas and grows in open, sunny locations such as rocky slopes.
- Oleander: It contains cardiac glycosides in its leaves, stems and flowers. Symptoms include nausea, irregular heart rhythms and seizures. In Arizona, oleander is a common landscaping plant.
What is the most poisonous plant in Arizona?
One of the most dangerous plants in Arizona is water hemlock, also known as cowbane.
Water hemlock is one of the most toxic plants in North America and contains the deadly toxin cicutoxin. Ingestion of even small amounts of water hemlock can lead to seizures, respiratory failure and death.
This plant is particularly hazardous because it can be mistaken for edible plants such as wild parsnip or celery.
What does 'toxic plant' mean?
A toxic plant can have varying degrees of effects, from mild to fatal, on people and animals.
“First of all, the word toxic. It's like, well, to who, because there are some plants that a bird can eat but a mammal cannot, or a certain insect could eat it or another insect couldn’t,” said Stromberg. “But the general point is that toxicity can vary widely from just a mild stomach ache or a mild headache.”
Familiarize yourself with the local flora and exercise caution when exploring the outdoors to avoid accidental exposure to poisonous plants. Be informed, but don't overreact.
“There's so much fear in our society and fear of the natural world that is pervasive, and I sort of want to counter that with the joy benefits. The risk of someone dying from a plant in your yard is low,” said Stromberg.
What is the most poisonous plant in the desert?
One of the most poisonous plants in the desert is the water hemlock, typically found in moist soils along the edges of standing or running water.
Water hemlock contains the deadly toxin cicutoxin, which affects the central nervous system, according to Banner Health. Ingestion of any part of the water hemlock plant, can lead to seizures and respiratory failure.
Another highly poisonous desert plant is jimsonweed, also known as devil's snare or thornapple. It grows in fields and waste areas. If ingested it can cause symptoms such as hallucinations, blurred vision, increased heart rate and difficulty urinating.
Is there poison ivy in Arizona?
Yes, poison ivy is common in Arizona, particularly in cooler, damper and more forested areas such as Flagstaff and other mountainous areas.
What is the stinging plant in Arizona?
The desert nettle, or desert stingbush, is not a true nettle but it can cause intense stinging and itching upon contact with its tiny, hairlike stinging structures.
Another class of plants to watch out for is the spurge family, which includes leafy spurge and spotted spurge. These plants contain a milky sap that can cause skin irritation, blistering and inflammation.
Does poison hemlock grow in Arizona?
Yes, poison hemlock grows in Arizona. It is found in various habitats across the state, including fields, roadsides, ditches, waste areas and along streams and waterways. It is native to Europe and was introduced to North America, where it has become naturalized in many regions.
All parts of poison hemlock are poisonous. Ingestion of even small amounts can lead to nausea, vomiting, abdominal pain, dizziness and respiratory paralysis.
How do you know if a plant is poisonous?
Identifying whether a plant is poisonous requires careful observation and knowledge of common toxic plants in your area.
Study plant features such as leaves, flowers, stems, berries and roots, looking for possible indicators like shiny or waxy leaves, brightly colored berries, thorns, spines and milky sap, though not all toxic plants have these traits.
If you have the time and means, Stromberg recommends taking a botany class. If that's not an option, use field guides, plant identification books and reputable online sources, such as The University of Arizona's Poison and Drug Information Center or Backyard Gardener for accurate identification.
What plants are poisonous to touch?
Chew and Stromberg said that some plants, such as poison ivy, have oils or sap that can cause irritation and prickly plants can pierce the skin, but it's rare for mere contact to cause severe reactions. And some plants have photoactivated toxins, meaning they cause a reaction when exposed to sunlight after contact.
“There could be a photosensitivity involved if you're touching the plant and you're in the sun. This happened to me once,” said Stromberg.
One common example of a plant with photoactivated toxins is the giant hogweed, which can cause severe skin irritation and blistering if you touch it and then are exposed to sunlight. Other such plants include wild parsnip, certain species of limes and figs.
Cactus spines are not toxic, but getting pierced by a jumping cholla, prickly pear or other cactus spine can be painful and could lead to infection. If you get stuck by a cactus needle, wash the affected area with soap and water and seek medical attention if any adverse symptoms develop.
What plants are toxic to dogs in Arizona?
Some of the most notable toxic plants for dogs in Arizona, according to CentralPet.com, a dog day care and training service in Tucson, include:
- Sago palm: All parts of the sago palm contain a toxin called cycasin, which can cause severe liver damage and even death in dogs if ingested.
- Oleander: Oleander is a highly toxic plant that contains cardiac glycosides, which can cause vomiting, diarrhea, heart irregularities and death in dogs if ingested in sufficient quantities.
- Desert rose: Desert rose, also known as mock azalea, contains cardiac glycosides. Eating desert rose can cause vomiting, diarrhea and heart irregularities in dogs.
- Lily species: Many species of lilies, including Easter lilies, tiger lilies and daylilies, are toxic to dogs and can cause kidney failure if ingested.
- Castor bean plant: Ricin in the seeds of the castor bean plant can cause vomiting, diarrhea, abdominal pain and kidney failure in dogs.
- Dumb cane: Dumb cane plants contain insoluble calcium oxalate crystals, which can cause oral irritation, drooling and difficulty swallowing.
- Agave: Agave plants contain saponins, which can cause gastrointestinal upset, including vomiting and diarrhea, in dogs.
Do dogs know to avoid toxic plants?
Some dogs may naturally avoid toxic plants due to their bitter taste or unpleasant smell, but many dogs do not recognize the danger and may be curious to investigate or even eat toxic plants. Some dogs, especially bored ones, may be attracted to certain plants' texture, scent or appearance.
“If you have a dog, make sure their life is enriched enough that they're not just so desperate they just have nothing to do and they eat any plant that is near them,” said Stromberg.
Factors that make a dog more likely to eat a toxic plant include their breed, age, personality, training and environment. Puppies and younger dogs may be more curious and exploratory, putting them at higher risk.
To help prevent accidental ingestion of toxic plants, train your dog to avoid plants and discourage it from chewing on or eating unfamiliar vegetation.
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