Last Updated on August 20, 2020 by Kimberly Crawford
Lilies, castor beans, cycad palms, rhododendrons, azaleas, laurels, yews, crocuses, foxgloves and oleanders are among the most common poisonous plants for cats and dogs.
Many of the plants kept in homes and gardens contain substances which can be extremely toxic when ingested by pets. Some of the most poisonous varieties can cause severe illness and death for dogs and cats even when very small amounts of the plant are ingested.
Lily Plants are Poisonous for Dogs and Cats
Lilies are among the most common of the poisonous plants for cats. Toxic lilies in the genus Lilium include Easter lilies (L. longiflorum), tiger lilies (L. lancifolium) and stargazer lilies (L. auratum). Some species of day lilies (Hemerocallis) are also toxic for cats.
Lily plants are poisonous because they cause kidney damage. Symptoms can occur within hours of ingestion of the plant and include:
- vomiting
- lack of appetite
- lethargy
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Castor Beans are Toxic to Pets
The castor bean plant (Ricinus communis) contains a toxic substance known as ricin. Ricin can be found in all parts of the plant but is particularly concentrated in the castor bean. A single bean can be deadly for a dog.
Symptoms of castor plant or castor bean toxicosis include:
- vomiting
- diarrhea, often bloody
- excessive salivation
- excessive thirst
- lack of appetite
- abdominal pain
- weakness
- muscle twitching
- seizures
- tremors
- incoordination
- coma
Poisonous Cycad Palm Plants and Pets
Cycad palms such as the sago palm (Cycas revoluta) and the false sago palm (C. circinalis) contain the toxin cycasin. The entire plant is poisonous but the seeds are especially toxic.
Symptoms of poisoning with cycad palms include:
- vomiting
- excessive salivation
- excessive water consumption
- lack of appetite
- diarrhea or constipation
- icterus (yellow coloration of the skin and gums)
- neurological signs such as seizures
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Rhododendron, Azalea and Laurel Plants are Poisonous for Small Animals
Many of the plants in the Ericaceae family are toxic for pets. These plants include:
- Rhododendron species (rhododendron, azalea, rosebay)
- Kalmia species (laurel)
- Leucothoe species (black laurel, fetterbush)
- Lyonia ligustrina (maleberry, staggerbush)
- Pieris japonica (Japanese pieris)
- Ledum glandulosum (Labrador tea)
Symptoms of poisoning with these plants include:
- vomiting
- diarrhea
- excessive salivation
- pneumonia, caused by aspiration
- irregular heart beat
- depression
- incoordination
- weakness
- seizures
Yew Plants Toxic to Dogs and Cats
Yew plants of the genus Taxus contain various toxins known as taxane derivatives or taxines. All parts of the yew plant are poisonous and death can occur suddenly after ingestion, with no preliminary signs. When seen, symptoms include:
- vomiting
- neurological signs, such as trembling, incoordination and difficulty breathing
- slow heart rate and heart failure
Autumn Crocuses and Plant Toxicities for Dogs and Cats
Autumn crocuses (Colchicum autumnale) and showy autumn crocuses (Colchicum speciosum) contain colchicine and similar alkaloids throughout the plant with the highest concentrations of the poison in the flower, the corm and the seeds.
Symptoms of poisoning with the plant may take 12 to 24 hours to manifest and include:
- excess salivation
- depression
- vomiting
- diarrhea
- abdominal pain
- weakness
- paralysis
- collapse
Toxic Foxglove Plants and Pets
Foxglove plants found in the United States are the common or purple foxglove (Digitalis purpurea), the Grecian foxglove (D. lanata) and the straw foxglove (D. lutea). These plants contain toxins known as cardenolides such as digitalis.
Symptoms normally seen with foxglove toxicity in dogs and cats are:
- gastrointestinal irritation evidenced by vomiting, diarrhea, excessive salivation and lack of appetite
- irregular heart rhythms
Lily of the Valley Toxicity in Dogs and Cats
Lily of the valley (Convallaria majalis ) plants contain a cardenolide toxin similar to that seen in foxglove. Symptoms seen with lily of the valley poisoning are similar to those in foxglove poisoning. Sudden death with no prior symptoms has been reported.
Oleander Poisoning in Dogs and Cats
The oleander plant (Nerium oleander) is also known as the laurel rosa, the laurel blanco, the laurel colorado and the rosa laurel.
These plants contain a cardiac glycoside poison which produces symptoms similar to those seen with foxglove poisoning. Oleander poisoning is often caused by the ingestion of dead or dried leaves which apparently are more palatable to animals than the green leaves.
Yesterday, Today and Tomorrow Plants and Poisoning in Dogs and Cats
The yesterday, today and tomorrow plants (Brunfelsia australis and B. grandiflora) contain a neurotoxin known as brunfelsamidine which causes seizures when ingested.
All parts of the plant are toxic. Coughing, gagging and an abnormal movement of the eyes (called nystagmus) occur within minutes to hours after ingestion, followed by tremors and seizures.
Dogs and cats are often found chewing on or ingesting plant material. Unfortunately, many of these plants have the potential to be poisonous to both cats and dogs. Some of the most toxic plants are commonly grown as houseplants or garden ornamentals.
