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Most Dangerous Plants

Azalea, Rhododendron (Rhododendron spp.)

Rhododendron species contain Grayanotoxin which affect sodium channels in cell membranes, leading to neurologic, gastrointestinal, and cardiovascular dysfunction. Grayanotoxins are found in all parts of the plant. As few as two leaves may cause serious poisonings. Clinical signs in dogs and cats include vomiting, diarrhea, abdominal pain, weakness, depression, cardiac arrhythmias, hypotension, shock, cardiopulmonary arrest, pulmonary edema, dyspnea, CNS depression, seizures, and death. Signs generally occur within 4-12 hours of ingestion and may persist for several days.

Cardiac Glycoside-Containing Plants

Hundreds of cardiac glycosides have been identified in plants, the most commonly known is digitalis, which has been used medicinally in human and veterinary medicine for many years. All parts of cardiac glycoside containing plants are toxic and even small amounts can cause significant clinical sign, including death. These include oleander (Nerium oleander), lily-of-the-valley (Convallaria majalis), foxglove (Digitalis purpurea), certain milkweeds (Aesclepias spp.), and squill (Virginea maritime.) Clinical signs seen most commonly involve the gastrointestinal tract and cardiovascular system and generally develop within several hours of ingestion and signs may persist for 1-3 days.

Castor Beans (Ricinus communis)

The castor bean plant is used as a decorative plant and oil extracted from the seeds is used in industry and medicine. The toxic principle is ricin, which is one of the most potent toxins known. All parts of the castor bean plant are toxic, but the seeds contain the highest concentration of ricin and are most commonly associated with poisoning. Damage to the seed coat is required in order to allow the ricin to be available for absorption.



Cycad Palms (Cycas, Zamia)

These ornamental plants are found generally in tropical to subtropical climates, but may also be grown as houseplants in more temperate climates. Cycasin is considered to be the toxic principle that is responsible for the hepatic and gastrointestinal signs generally seen with toxicosis. Most parts of the plant are toxic, but the seeds (nuts) contain a higher concentration of cycasin and are more often associated with toxicosis in small animals. Ingestion of one or more seeds has resulted in severe signs and death in dogs.



Lilies

Easter lilies (Lilium longiflorum), tiger lilies (Lilium tigrinum), rubrum or Japanese showy lilies (Lilium speciosum and Lilium lancifolium), and various day lilies (Hemerocallis species) can cause acute renal failure and death in cats. The toxic principle is unknown. Even minor exposures (a few bites on a leaf, ingestion of pollen, etc.) may result in toxicosis. All feline exposures to lilies should be considered potentially life-threatening. Affected cats often vomit within a few hours of exposure to lilies, but the vomiting usually subsides after a few hours, during which time the cats may appear normal or may be mildly depressed and anorexic. Within 24 to 72 hours of ingestion, oliguric to anuric renal failure develops, accompanied by vomiting, depression, anorexia, and dehydration.