It’s easy to take our houseplants’ natural defense mechanisms for granted. After all, we’re rarely subjected to the pain and discomfort that can result from eating part of a toxic plant. But the same can’t be said for our beloved pets.
Part of being a responsible pet owner is ensuring your home is free of potentially dangerous plant life. The sad reality is that most houseplants are toxic to some extent.
In this article, I’ve listed 20 of the most toxic houseplants to cats (as well as dogs and humans) and offered some expert advice for protecting your loved ones.
What Makes Houseplants Toxic?
Plant toxicity usually comes from chemical compounds contained within different parts of the plant. Some species contain toxins only in select areas. Others are toxic through and through.
In rare cases, toxicity symptoms can arise just from touching a plant — e.g., poison ivy. More often than not, however, it takes ingesting part of the plant to experience symptoms.
It’s also important to remember that ‘toxic’ does not always equal fatal. The vast majority of toxic houseplants will cause pain and discomfort if ingested but are not deadly under normal circumstances. But it’s still important to protect our pets from these noxious plants whenever possible.
Toxic Substances in Houseplants
There are several common plant compounds that can cause negative reactions in humans and animals that come into contact with them and each functions a bit differently.
Saponins
Saponins are a category of glycosides present in — as far as we know — all plants. Only plants that contain high amounts of saponins are generally considered to be toxic.
In nature, saponins are believed to protect plants against pests and diseases and deter herbivores from feeding on them.
Insoluble Calcium Oxalates
Calcium oxalate crystals are incredibly small and sharp (I like to compare them to fiberglass but even smaller). When the crystals come into contact with your skin, mouth, or digestive tract, they create micro-tears. This causes acute pain and swelling.
The term ‘insoluble’ is important because it means that the calcium oxalate crystals cannot enter the body as a whole. If ingested, they simply pass through the digestive tract.
Soluble calcium oxalates — present in plants like rhubarb and shamrocks — are capable of passing into other parts of the body, like the renal system, and causing severe damage. Ingesting soluble calcium oxalates can be fatal, especially for cats.
Proteolytic Enzyme
Proteolytic enzymes are naturally occurring enzymes that break down proteins. Such enzymes are beneficial in certain circumstances — e.g., they play a crucial role in human and animal digestive systems — but can cause irritation in high doses.
Irritant Sap
In most cases, a reaction will only occur if irritant sap is released by a damaging part of the plant. This can happen during routine care or when a pet decides to bite into the plant.
While these reactions are normally mild and resolve after a few days at most, some people and animals may have more severe allergic reactions to irritant sap.
Cycasin
Cycasin is a carcinogen and neurotoxin present in all cycads. Cycads are a unique group of plants that have been around since prehistoric times. The Sago Palm is the most well-known example.
There’s currently no established theory explaining why cycads produce this potent toxin. All parts of the plant contain cycasin but it is usually most concentrated in the seeds.
Plant Toxicity Categories
Toxic plants are often categorized by the severity and type of symptoms caused. I’ve outlined these categories below based on info published by the University of California.
While these categories are fairly universal, keep in mind that some organizations have slightly different guidelines for which plants fall into which categories. Also note that toxicity classifications are generally based on human biology, so these levels aren’t always accurate for cats, dogs, and other animals.
- Level 1 — These plants are capable of causing serious illness and even death if ingested. Many Level 1 plants affect heart and brain function, as well as other vital biological systems.
- Level 2 — These plants can cause mild or moderate illness when ingested. Symptoms are often limited to vomiting and/or diarrhea but may vary.
- Level 3 — These plants contain calcium oxalates that cause irritation when ingested. Symptoms include pain and swelling of tissues that come into contact with the calcium oxalates but normally subside once the crystals leave the body.
- Level 4 — These plants may cause skin irritation if various parts of the plant, including the sap, are touched. Symptoms are very mild except in cases of allergies or other sensitivities.
List of Toxic Houseplants
1. Aglaonema
- Common Names: Chinese Evergreen, Philippine Evergreen
- Scientific Name: Aglaonema commutatum
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
The Chinese Evergreen and other members of the Aglaonema genus contain insoluble calcium oxalates. Both humans and animals are sensitive to calcium oxalate crystals, so care should be taken to keep these houseplants away from pets and children.
Oxalate crystals are largely concentrated in the plant’s leaves and stem. However, chewing on any part of the plant can cause acute pain and swelling.
2. Alocasia
- Common Names: Elephant Ear
- Scientific Name: Alocasia spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
Alocasia houseplants, most commonly known as Elephant Ears, contain insoluble calcium oxalates that can cause moderate discomfort in humans and pets when ingested. Symptoms usually resolve after several hours or once the oxalate crystals leave the body.
The Alocasia genus includes species like Giant Taro that are traditionally used as food crops. While careful preparation may reduce the number of calcium oxalates in these plants, exposure is still possible when eating foods like poi.
3. Anthurium
- Common Names: Laceleaf, Flamingo Flower
- Scientific Name: Anthurium spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
Anthurium flowers belong to the Araceae family. All plants belonging to this family, which includes many other houseplants on this list, contain insoluble calcium oxalates.
The insoluble calcium oxalates are present in the plant’s sap. While the sap is contained in all parts of the Anthurium plant, it generally won’t cause irritation unless you or your pet comes in direct contact with it. Keep these plants out of reach of curious children, cats, and dogs.
4. Arrowhead
- Common Names: Arrowhead Plant, Arrowhead Vine
- Scientific Name: Syngonium spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
Arrowhead houseplants, or species within the genus Syngonium, contain insoluble calcium oxalates. All parts of the Arrowhead plant contain some amount of oxalate crystals and will cause mild irritation if ingested.
There are several different houseplants that look like Arrowheads — some are even sold as ‘Arrowheads’ by nurseries and gift shops. For this reason, I always recommend using a plant’s scientific name for toxicity information rather than relying on common names.
5. Aucuba japonica
- Common Names: Gold Dust Plant, Japanese Laurel, Spotted Laurel
- Scientific Name: Aucuba japonica
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Aucubin
- Symptoms: Nausea, vomiting, diarrhea
Although more commonly grown as an outdoor shrub the Gold Dust Plant, also known as Spotted Laurel, also adapts to being grown as a houseplant. It is slightly toxic to both humans and pets. All parts of the plant contain a unique chemical compound called aucubin, which causes stomach upset if ingested.
The bright red berries are also poisonous if eaten. Fortunately, Gold Dust Plants rarely flower indoors and, if they do, still require a second, male plant to produce any fruit.
6. Caladium
- Common Names: Angel’s Wings, Elephant Ears
- Scientific Name: Caladium spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates, asparagine
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
Houseplants within the Caladium genus go by many common names, including Elephant Ears and Angel’s Wings. All species within this genus contain insoluble calcium oxalates and an amino acid called asparagine.
Ingesting any part of a Caladium plant can release calcium oxalate crystals that irritate the mouth and digestive system.
Consuming large amounts of asparagine may lead to liver dysfunction, pancreatitis, and other serious complications. However, you or your pet would likely need to ingest an incredible amount of Caladium to be at risk of such conditions.
7. Dieffenbachia
- Common Names: Dumb Cane
- Scientific Name: Dieffenbachia spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates, proteolytic enzyme
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
Members of the Dieffenbachia genus — the most popular example is Dumb Cane — contain irritating calcium oxalate crystals within their sap.
According to the National Capital Poison Center, these houseplants also release proteolytic enzymes. The combination of the two mild toxins can produce more severe symptoms than calcium oxalate alone.
8. Dracaena
- Common Names: Corn Plant, Dragon Tree, Lucky Bamboo
- Scientific Name: Dracaena spp.
- Toxicity: Cats, Dogs
- Toxic Substance: Saponins
- Symptoms: Nausea, vomiting, diarrhea
This is an extremely diverse genus containing popular houseplants like Lucky Bamboo, Corn Plant, and Dragon Tree. All Dracaena species possess saponins that are toxic to cats and dogs when ingested.
Houseplants within the genus Cordyline are frequently mislabeled as Dracaena species. Cordyline plants also contain saponins and present the same toxicity risk to pets.
9. Fiddle Leaf Fig
- Common Names: Banjo Fig
- Scientific Name: Ficus lyrata
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Irritant sap, insoluble calcium oxalates
- Symptoms: Skin irritation, oral pain, and swelling
The sap of the Fiddle Leaf Fig contains high concentrations of insoluble calcium oxalates that can cause mild pain and swelling within any tissue they come into contact with.
While most cases of exposure to this irritant sap are the result of ingesting part of a Fiddle Leaf Fig leaf, all parts of the plant contain these oxalate crystals.
10. Ivy
- Common Names: English Ivy, Algerian Ivy, Japanese Ivy
- Scientific Name: Hedera spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Saponins
- Symptoms: Nausea, vomiting, diarrhea
Ivy (from the genus Hedera) is high in saponins. Note that there are several houseplants whose common names include ‘ivy’ that do not belong to this group.
Saponins tend to cause mild to moderate symptoms in humans, cats, and dogs who ingest them. Since these toxins are naturally very bitter-tasting, severe cases of poisoning are rare.
11. Jade Plant
- Common Names: Money Tree, Rubber Plant
- Scientific Name: Crassula ovata
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Saponins, unknown
- Symptoms: Nausea, vomiting, diarrhea
The Jade Plant, or Crassula ovata, is a popular succulent found in many homes. It is considered to be mildly toxic to people and extremely toxic to pets if ingested. It is recommended to wear latex gloves when handling or propagating Jade plants.
Interestingly, the exact cause of Jade’s toxicity isn’t completely understood. While some sources attribute its toxicity solely to saponins, it’s also believed that other compounds may be present within the plant that cause similar symptoms.
12. Oleander
- Common Names: Rose Laurel, Jericho Rose, Nerium
- Scientific Name: Nerium oleander
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Glycosides
- Symptoms: Nausea, vomiting, diarrhea, weakness, loss of coordination
Oleander, also known as Rose Laurel or Jericho Rose, is one of the most toxic plants grown ornamentally. The toxic glycosides contained within Oleander primarily affect the heart. Even just a single leaf can be deadly to a pet or small child if ingested.
Avoid keeping Oleander if any pets or children live in or frequently visit your home.
13. Peace Lily
- Common Names: Spathe Lily
- Scientific Name: Spathiphyllum spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
The Peace Lily contains insoluble calcium oxalates that will cause mild symptoms in any human, cat, or dog who ingests part of the plant.
Although Peace Lilies are toxic, they are far safer for pet cats than true lilies (Lilium spp.) and daylilies (Hemerocallis spp.). Plants within these families contain unidentified toxins that are often fatal if ingested.
14. Philodendron
- Common Names: Heartleaf Philodendron, Split-Leaf Philodendron
- Scientific Name: Philodendron spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
There are hundreds of different Philodendron species, many of which are grown as houseplants. All of these plants contain insoluble calcium oxalates.
Ingesting part of a Philodendron leaf, stem, or root is likely to cause short-term discomfort in the mouth and digestive system. Symptoms usually go away after a few hours.
15. Poinsettia
- Common Names: Christmas Flower, Flame-Leaf Flower
- Scientific Name: Euphorbia pulcherrima
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Irritant sap
- Symptoms: Mouth and stomach irritation, vomiting
Despite common misconceptions, there are no known cases of human or pet fatality caused by consuming part of a Poinsettia. The plant is only mildly toxic.
Poinsettias contain irritant sap that can trigger skin or oral irritation if touched. It can also cause indigestion if enough of the sap is eaten.
16. Pothos
- Common Names: Golden Pothos, Devil’s Ivy, Ivy Arum
- Scientific Name: Epipremnum aureum
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
The Golden Pothos and related houseplants all contain insoluble calcium oxalates. These irritating crystals are present in all parts of the Pothos plant.
Symptoms typically arise when part of the Pothos is ingested. However, mild skin irritation may also occur if you or a pet comes into contact with the plant’s sap.
17. Schefflera
- Common Names: Umbrella Tree, Parasol Plant, Octopus Tree
- Scientific Name: Schefflera spp.
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Insoluble calcium oxalates
- Symptoms: Oral pain and swelling, vomiting, trouble swallowing, drooling
The Umbrella Tree — commonly, Schefflera actinophylla or Schefflera arboricola — contains insoluble calcium oxalates. Ingesting part of this plant may cause acute swelling and discomfort.
The Schefflera genus is very diverse and, according to my research, some species may be more toxic than others. But you’re unlikely to encounter any other species than the two mentioned above as houseplants.
18. Snake Plant
- Common Names: Mother-in-Law’s Tongue, Viper’s Bowstring Hemp
- Scientific Name: Sansevieria trifasciata
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Saponins
- Symptoms: Nausea, vomiting, diarrhea
The snake plant, also known as Sansevieria trifasciata, is toxic to both humans and pets when ingested. This plant contains saponins, which cause vomiting, nausea, and stomach pains. If consumed in large quantities or in extreme cases, ingestion can lead to seizures or even death.
This plant is perfectly safe to handle but care should be taken to keep it out of reach of young children and pets.
19. Spider Plant
- Common Names: Airplane Plant, Ribbon Plant
- Scientific Name: Chlorophytum comosum
- Toxicity: Cats (very mild)
- Toxic Substance: Hallucinogenic compounds
- Symptoms: Mild stomach upset
To say that the Spider Plant is toxic to cats is mostly just a technicality. There are no known cases of serious symptoms or fatalities associated with cats ingesting this plant.
Spider Plants contain similar hallucinogenic compounds as catnip. Unlike catnip, however, ingesting part of a Spider Plant is also likely to cause mild stomach upset.
20. Sago Palm
- Common Names: Cycad, King Sago
- Scientific Name: Cycas revoluta
- Toxicity: Humans, Cats, Dogs
- Toxic Substance: Cycasin
- Symptoms: Vomiting, increased thirst, bloody stool, jaundice
All parts of the Sago Palm are toxic due to the presence of a dangerous toxin called cycasin. When ingested, this compound can affect the liver and nervous system and cause severe digestive distress in as little as 15 minutes.
Consuming any part of this plant is potentially fatal. Sago Palms are not recommended for homes with pets or young children.
Reducing The Risk Of Poisoning
Most cases of houseplant toxicity are the result of easy access. While some cats will go to great lengths to access any plants in the home, you can reduce the risk of poisoning by following the tips below:
- Remove plants with high toxicity levels from the home
- Keep mildly toxic plants out of reach of pets and young children
- Use pet-safe deterrents like citrus oil to prevent chewing on houseplants
- Provide pet-safe plants — e.g., cat grass — as an alternative for chewing behavior
What To Do If Toxicity Symptoms Are Present
If your cat or dog shows severe signs of toxicity, immediately get in touch with an emergency veterinarian for further guidance. For mild symptoms of plant toxicity, follow the steps below:
- Identify the type and severity of the symptoms. Call your local poison hotline or emergency veterinarian immediately if serious symptoms are present.
- Locate the offending houseplant. Examine the plant to determine how much was potentially ingested. Make note of the plant species and take a photo for future reference.
- Contact your pet’s primary veterinarian with the above information.
- Unless otherwise advised by a vet, provide a clean source of drinking water.
- Monitor for new or changing symptoms until the toxicity subsides.
You should never induce vomiting unless specifically instructed to do so by a veterinarian.
You might also like to read Are ZZ Plants Toxic to Cats, Dogs, or even Humans?
Citation
MSD Veterinary Manual – Houseplants and ornamentals
UWEC ENPH Environmental Toxicology – Toxic Houseplants
The University of Lancaster – Toxicity of Common Houseplants
ASPCA – Plants Toxic to Cats
ASPCA – Plants Toxic to Dogs
University of California — Plant toxicity levels
National Capital Poison Center — Dieffenbachia toxicity
Colorado State University — Oleander toxicity
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.
