8 Most Dangerous Plants for Cats and Dogs

By Dr. Tina Wismer

Many common plants, both in the house and the yard, can be toxic to our pets, including some that can still be found this time of year, either because they are being brought in from outside or because they are popular in holiday displays or decorations. Some toxic plants only cause mild stomach upset, while others can be poisonous. To make things even more confusing, some plants are safe for some species while deadly for others. As a pet owner, it is important that you be familiar with the most dangerous of the toxic plants.

SEE ALSO: 10 Most Dangerous Foods for Your Pet

ThinkstockGrayanotoxin Plants
Grayanotoxins can cause vomiting, seizures and cardiac arrest. Sources include rhododendrons, azaleas, laurels and Japanese pieris. These are typically outdoor plants, but they are highly toxic in all species and deserve extra caution.

Sago Palms
Sago palms can be found as outdoor ornamental plants in warm climates or as houseplants in cooler climes. Ingestion of sago palm plants can cause liver failure and death in dogs and cats. All parts of the plant are toxic, with the seeds having the highest concentration of toxin. One seed can kill a dog. within 24 hours, and animals become depressed and may start to seizure. This plant is one of the most toxic, with a mortality rate of around 30 percent.

See Also: 26 Common Household Items Poisonous for Pets

Cardiac Glycoside Plants
Plants containing cardiac glycoside include oleander, foxglove and lily of the valley. These glycosides slow down the heartbeat and can even stop it. These plants are toxic in all species. These are typically outdoor/landscape plants, but the popular and beloved lily of the valley is a common bouquet flower for winter arrangements, weddings and other holiday gatherings.

ThinkstockJapanese Yew
Yews are commonly used as landscaping plants as they stay green year-round. A pet looking for a bit of winter green may be tempted to take a nibble. Yews contain compounds that have a direct action on the heart. The toxins can cause an irregular heartbeat or even stop the heart. All parts, except for the ripe berry (the fleshy red structure surrounding the seed), are toxic. Sudden death can occur within hours of ingestion.

Castor Bean
Ricinus communis (commonly known as the castor bean) contains ricin, which can be highly toxic. Ricin causes multiple organ failure. Ricin is found throughout the plant, but the highest levels are found in the seeds. The seed coat must be damaged to release the toxins, so animals who swallow the seeds whole may not get sick. The mortality rate in dogs is about 9 percent. These beans are also commonly used in many rustic-type ornaments and jewelry.

ThinkstockAutumn Crocus
Autumn crocus contains chemotherapy-like compounds that attack rapidly dividing cells in the body. Ingestion can cause vomiting, diarrhea, weakness and possible death. Do not confuse this flower with the innocuous spring crocus, which is not toxic.

Hops are used in beer brewing, so home brewers need to be aware of this toxic plant. Ingestion of hops by dogs causes their body temperature to skyrocket. Signs can be seen within hours. Dogs become agitated and begin to pant. Their body temperature can get high enough to kill them - up to 108 degrees Fahrenheit.


Members of the true lily family (Lilium and Hemerocallis) have been shown to cause kidney failure in cats. Some examples of true lilies include Easter lilies, tiger lilies, rubrum or Japanese showy lilies, and day lilies. Even a small amount of exposure (a few bites on a leaf, ingestion of pollen, etc.) may result in kidney failure. Cats often vomit within a few hours of exposure and stop producing urine within 72 hours. Cats who receive quick treatment (intravenous fluids for two days) have a good prognosis. Lilies are common in holiday flower bouquets and arrangements, as are popular lily-like holiday flowering bulbs, such as amaryllis, which can also be toxic to pets.

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