Poisonous Plants of Hawaii

There’s a price to pay in paradise. Hawaii, known for its lush vegetation, striking topography and tropical drink concoctions, also plays host to a variety of poisonous plants. While some plants may only cause minor gastrointestinal problems or skin irritation, others are highly toxic and can result in vomiting, delirium, blindness, respiratory paralysis or death. One species, the castor bean plant (Ricinus communis), derives its name from the ricin poison in its seeds — the same substance that was detected on envelopes sent to President Barack Obama and U.S. Senator Roger Wicker in 2013.

Some plants are toxic solely through touch, especially if a plant has spiny fruit, milky sap, hairy leaves, or an atypical fruit shape. Scores of Hawaiian plants have varying degrees of toxicity, including parts of some edible plants like the mango and cashew. Animals are not immune to the toxic effects of many of these plants which can cause them to develop serious symptoms or die if ingested.

Often found in disturbed areas, such as the edges of roadsides, Apple of Sodom (Popolo kikania) is a highly toxic common shrub. It is related to both the nightshade — another poisonous plant — and the tomato, which is, of course, quite edible. All parts of this plant are toxic and can cause tremors, paralysis, coma and death. Angel's trumpet is toxic, but indigenous people and even modern-day doctors have used the plant’s compounds as medicine. It is also known for its hallucinogenic qualities. Ingestion of any of this plant’s parts can cause blurry vision, restlessness, disorientation, seizures, respiratory failure or death among other symptoms. Dieffenbachia plants are common houseplants throughout the United States and are a frequent cause of poisoning in Hawaii. Touching these plants can cause burning and itching of the skin; if ingested, they may cause swelling of the mouth, tongue, lips and throat.

The evergreen pencil plant (Euphorbia tirucalli L.) is one of 8,000 species belonging to the Euphorbiaceae family. It sports slender, pencil-like stems that contain a caustic and poisonous white latex. It has a history of use as a rubber substitute and pesticide as well as to treat a variety of ailments. The latex can cause conjunctivitis of the eye and is also a co-carcinogen. Oleader (Nerium oleander) is a showy shrub with attractive clusters of flowers that contrast with its slender, elongated dark leaves. This plant's sap can cause an allergic reaction in some people. Ingestion may cause gastrointestinal upset and vomiting. It can also result in a slowed or irregular pulse. The resultant smoke from burning the plant may also be quite toxic.

The Kukui, or candlenut tree is the state tree of Hawaii. Found in damp lowland forests, this distinctive broad-branched tree has multiple historical uses including jewelry, fuel, medicine and lighting. All parts of the tree are poisonous. The seeds can cause vomiting and gastrointestinal problems. The physic nut tree (Jatropha curcas L) contains curcin, a highly toxic compound similar to ricin from the castor bean plant. Seed ingestion can prove fatal and the tree's sap can irritate the skin. On a more positive note, the seeds of this plant have shown promise as a biodiesel fuel due to their high oil content.