7 Surprisingly Common Plants That Are Poisonous to Pets

Written and submitted by guest author, Emily Jackson

Most pet owners know that some plants, including lilies, poison ivy, azalea, daffodil, and oak, are harmful to their cats and dogs. However, you may be shocked to find out that we are surrounded by surprisingly common plants that are poisonous to pets.

Always practice care when planting particular veggies, herbs, and flowers in your garden or windowsills to protect your beloved furry friends. If you can't live without some of the listed plants, be sure to supervise your animals carefully, especially curious cats.

Common Plants Poisonous to Pets

1. Aloe Vera

Among the most surprising is Aloe Vera, known as a plant highly beneficial for humans. While the plant’s internal gel is mostly harmless, its skin is toxic to both cats and dogs. Chemicals, saponins (glycosides), located in the skin of the leaf have antiseptic and cleansing properties in humans. Alternatively, these chemicals can cause vomiting, diarrhea, tremors, depression, lethargy, and extremely irritated skin in your pet.

Fortunately, symptoms are usually not severe, unless when your pet ingests a large piece of the plant. If you spot red urine along with other symptoms, take your pet to the vet right away.

2. Potatoes

Recently, the FDA (the US Food and Drug Administration) announced that DCM (canine dilated cardiomyopathy) was reported in dogs eating pet food containing potatoes and peas as primary ingredients.

This disease usually occurs in genetically prone breeds. However, veterinarians have discovered that a wide variety of dogs may become sick after eating food rich in this particular vegetable for long periods of time. Many common varieties of grain-free dog food are found to contain high quantities of potatoes.

Both potatoes and their stems/leaves contain highly toxic solanine that is poisonous to your pets. You should never feed a dog raw potatoes, and while cooking will reduce the level of this chemical, potential risks still exist. Instead, consider replacing standard potatoes with dog-approved, cooked sweet potatoes.

3. Oregano

Many of us grow oregano (Origanum vulgare hirtum) in our homes and gardens, but rarely are pet owners aware of how dangerous this particular plant is for their furry friends. Thankfully, nature stepped in to make this plant repellent to cats. Their sophisticated noses sense this fragrance at a level 1400% stronger than humans. The consumption of fresh oregano usually causes mild intestinal issues in both cats and dogs.

Additionally, the essential oil made of this plant contains gastrointestinal irritants, such as terpenoids and phenols. Avoid applying this oil to your cat directly since it is poisonous and its ingestion may lead to liver failure.

4. Hibiscus

In most cases, hibiscus is non-toxic for pets, but the Rose of Sharon (Hibiscus syriacus) is a type of hibiscus that can be harmful to your furry friend. If a dog ingests a significant amount of this hibiscus’ flower, they can experience nausea, diarrhea, and vomiting. No one knows the reason why some types of hibiscus are toxic while others remain non-toxic to canines. For cats both blossoms and stems of this hibiscus are poisonous.

5. Oleander

A few years ago, I brought oleander (Nerium oleander) seedlings from Greece. I have always adored that flower and wanted to grow it in my garden, but someone told me that it could hurt my pets. 

I learned that all parts of the oleander are highly toxic, and even small amounts may cause several health issues to a variety of species including dogs, cats, and even humans. These plants, especially the variety with red flowers, contain cardiac glycosides, which cause hypothermia, slow heart rate, arrhythmias, severe vomiting, lethargy, and tremors. In some cases, it can lead to death, though this is quite uncommon.

For several reasons, most people have never heard how dangerous this plant can be. This plant primarily grows in California and Hawaii, so most pet owners in the remainder of the country are unfamiliar with its characteristics. Thankfully, for most pets oleander is unattractive. 

If you plant or have this flower growing nearby, always monitor your pets so you can enjoy the fragrance and beauty of this exotic plant without worry.

 6. Marijuana 

 Pet poisoning by marijuana (Cannabis sativa) is one of the most common intoxications seen in veterinary practice, especially in dogs. Due to an increased level of cannabinoid receptors in the canine brain, they are particularly vulnerable. For both cats and dogs, most are exposed by nibbling dried leaves, consuming edibles and/or inhaling second-hand smoke.

 In Colorado, a state with legalized marijuana, within five years, two veterinary hospitals noticed that the frequency of marijuana poisoning in dogs has increased four times since the legalization legislation was passed.  

Ingesting these plants in any form may cause depression of the central nervous system and problems with coordination in your pet. In most cases, the animal will experience dilated pupils, increased heart rate, troubles with regulating temperature, vomiting, diarrhea, seizures, tremors, and even coma.

7. Tomato Plant

Common tomatoes (Lycopersicon spp) and its entire plant are poisonous for both cats and dogs. The unripe fruit, stems, and leaves contain alpha-tomatine and the same glycoalkaloid solanine as potatoes. These parts of the plant may cause intoxication when eaten in a considerable amount. Fortunately, poisoning by tomato plant is not typically fatal.

 Common symptoms include weakness, drowsiness, stomach pain, slow heart rate, and difficult breathing. Ripe tomato fruits themselves won't cause any problems in most cases.

The ASPCA (The American Society for the Prevention of Cruelty to Animals) provides long lists of plant poisonous to both cats and dogs. Make sure to learn more about the hidden dangers that might be in your own home. The best way to protect your pet from poisoning is to check plant lists before adding to your pet food or garden.

About the Author

My name is Emily Jackson. I am a writer, translator, veterinarian, humanitarian, and a passionate traveler. After playing with white bears and elephants in the Belgrade ZOO and dealing with Rabies virus in the Institute Pasteur, I enjoy writing. My five beasts are my ultimate love, including three cats (Clementine, Josephine, and Sophio) and their 'mom' American Stafford Terrier (Malena).