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What are poisonous plants in Arizona and the Southwest?

Michael Levine, MD, is medical toxicology fellow, Banner Poison & Drug Information Center.

Question: What can you tell me about poisonous plants in Arizona and the Southwest?

Answer: There are many different poisonous plants found throughout Arizona and the Southwest.  While a plant may be considered “poisonous,” however, there are significant degrees of toxicity.  Depending on the specific species various parts of the plant can be toxic. For example, in some plants the seeds are dangerous, while other plants the leaves or stalks may be toxic.

Plants, such as the foxglove, oleander, or zygadenus are potentially dangerous to the heart, and can cause various abnormal heart beats.  Some commonly used heart medications are actually derived from the foxglove plant.  Consumption of these plants can cause nausea, vomiting, visual changes, abnormal cardiac beats, and potentially even death.  

Other plants, such as the dumbcane is more of an irritant, rather than a direct toxin.  Chewing on the leaves produces some local swelling and an intense burning pain on the tongue, but do not produce systemic toxicities.

Jimsonweed is a plant that is commonly abused by teenagers for its hallucinogenic properties.  While patients can develop hallucinations as a result of ingesting these plants, the hallucinations are typically not what patient’s desired.  In addition, patients can get many other complications from ingesting the plant, including fast heart rate, fever, confusion, and impaired ability to urinate.

The Texas mountain laurel is another plant commonly found throughout Arizona.  Similar to the castor bean, most patients will develop only vomiting and diarrhea.  Some patients, however, can develop significant toxicities, and while very uncommon, can theoretically be fatal if massive amounts are ingested.

Many other plants, such as the candelabras cactus and mistle toe can cause vomiting and diarrhea when ingested.

Perhaps one of the most commonly encountered plants, however, is poison oak or poison ivy.  Recognized best by the pneumonic “leaves of three, let them be,” these plants produce local irritation, rash, and pain in the areas of the body that come in contact with the plant’s oil. 

Thus, while many plants are beautiful and most are non-toxic, there are several potential plants indigenous to Arizona that are associated with potential harm when ingested.  As with most things, it is best not to eat plant or shrubs that are growing in the wild, unless one knows for sure the plant is safe.  Despite having many potential toxic plants, it is important to remember that ingestion of most plants result in little or no toxicity.

Photographs of many commonly encountered plants can be found on the website of the Desert Botanical Garden or at the Arizona Native Plant Society.

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