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Outdoor Plants Poisonous to Cats

Outdoor Plants Poisonous to Cats 

Updated on November 03, 2021
Reviewer Profile Photo
Reviewed by Dr. Jennifer Coates
DVM
cat outside with owner

Watching a cat outdoors happily chasing butterflies and shadows can be delightful. That’s likely why about 40% of US cat parents let their felines outdoors at least some of the time. However, the outside world isn’t without risks. One of the many risks to cats who go outdoors is exposure to toxic plants. It’s important to ensure your yard is safe for cats in all aspects—including being free of any outdoor plants toxic to cats.  

Since we mostly choose plants based on what’s eye-catching and safe for humans, it can be hard to recognize flora that’s dangerous to your feline. That’s why we compiled a detailed list of many outdoor plants that are toxic to cats. 

Autumn crocus

autumn crocus

Don’t let the delicate purple flowers fool you—autumn crocus is one of the more deadly outdoor plants toxic to cats and humans alike. All parts of the plant contain the alkaloid colchicine, which can cause kidney and liver damage, vomiting, diarrhea (which may contain blood), respiratory failure, seizures and death if ingested. Symptoms can develop immediately or be delayed for several days, beginning with gastrointestinal distress and progressing to bloody vomiting, diarrhea, seizures, labored breathing and eventually respiratory failure. Seek veterinary attention immediately if you suspect your cat has ingested autumn crocus.  

Bird of paradise

bird of paradise plant

This is one bird your kitty doesn’t want to eat. Residents of the warmer parts of the US will be glad to know that birds of paradise (Strelitzia reginae) are only mildly toxic to cats but they can cause gastrointestinal problems if ingested. Keep an eye out for digestive issues if you suspect ingestion.  

Buttercup

buttercup flower

In some parts of the country, buttercups seem to grow everywhere. Luckily, this is one of the plants toxic to cats that isn’t very tasty. Buttercups are very bitter, and the toxin they contain—protoanemonin—can even cause blisters in the mouth. The toxin, which is mostly concentrated in the flowers, also irritates the gastrointestinal tract. If your kitty does eat enough buttercups, you might notice drooling, lack of appetite, vomiting, diarrhea, weakness, stumbling or ulcers in the mouth.  

Crysanthemum

crysanthemum plant

The popular Chrysanthemum family, which includes daisies and mums, are all plants that are toxic to cats. The leaves and stems contain pyrethrins—naturally occurring pesticides also found in some flea & tick medications for pets. While they do a great job protecting plants from insects, they can be poisonous to cats if ingested. Symptoms include hypersalivation, drooling, vomiting, diarrhea, lethargy, lack of appetite, skin irritation and stumbling.  

Daffodil

daffodil flower

With their buttery yellow flowers, daffodils may look tasty, but your kitty’s stomach won’t like this plant. All parts of the plant are toxic to cats due to the chemical compound lycorine—although it’s most concentrated in the bulbs. Lycorine is found in several plants poisonous to cats—including bush and surprise lilies—and commonly causes drooling, vomiting and diarrhea. Ingestion of large amounts can cause low blood pressure, muscle tremors, and heart rhythm abnormalities  

Foxglove

foxglove plant

Foxglove is extremely poisonous to cats—even the water from a vase filled with its beautiful, trumpet-like flowers can be toxic. All parts of the plant contain cardiac glycosides, an enzyme inhibitor that affects the heart. The initial symptoms are vomiting, weakness or dizziness and collapse. Without immediate treatment, heart failure can occur.  

Hyacinth

hyacinth flower

Hyacinths are one of the outdoor plants toxic to cats that contain toxins called tulipalin A and B. These toxins are found throughout the plant but mostly concentrated in the bulbs. Hyacinth can cause vomiting, diarrhea, drooling, tremors and listlessness. Keep your kitty away from this deadly cousin of the tulip.  

Hydrangea

hydrangea plant

Are hydrangeas poisonous to cats? Unfortunately, yes. They’re one of the most popular outdoor plants, thanks to their versatility, hardiness and beauty—but also can make cats sick. Hydrangeas contain cyanogenic glycosides. While every part of the plant is bad, the leaves and flowers are the worst for your kitty. Symptoms after ingestion include exhaustion, vomiting and diarrhea.  

Iris

iris flower

When listing what flowers are poisonous to cats, irises won’t be found near the top. However, they contain irritants that cause a lot of discomfort for your cat inside and outside. If your cat ingests irises, you might notice skin irritation, mouth ulcers, abdominal pain, vomiting or diarrhea. All parts of the plants contain these compounds, but the bulbs are the most toxic.  

Lily

lily plant

Lilies top every list of plants poisonous to cats. Certain varieties are more toxic than others—Peace lilies, Peruvian lilies and calla lilies should only cause minor symptoms, while true lilies like Asiatic, Easter, Japanese show, stargazer, tiger and daylilies can be deadly. Experts don’t exactly know what makes them toxic, but it’s been proven that ingesting any part of a true lily—even licking pollen from the fur or drinking water from a vase—can cause kidney failure. The first symptoms can include lethargy, loss of appetite, vomiting and increased thirst and urination and you’ll need to make an immediate trip to your veterinarian.  

Lily of the valley

lily of the valley flower

Despite its name and sweet, fresh scent, Lily of the valley is technically not a lily—it’s actually part of the asparagus family. Still, it is one of the plants toxic to cats that contains cardiac glycosides, which affect the heart. Every part of the plant is harmful to cats. If ingested it can cause diarrhea, vomiting, seizures, tremors and a slow or irregular heartbeat.  

Oleander

lily plant

Add oleander to the list of plants that are toxic to cats because it contains cardiac glycosides—a toxic compound fairly common in many outdoor plants. All parts of the plant are poisonous, and red varieties seem more harmful than others. Like other plants with cardiac glycosides, oleander can cause vomiting, diarrhea, seizures, tremors and heart abnormalities.  

Peony

peony flower

Peonies are often pretty in pink, but they’re anything but dainty. They contain paeonol, a phenolic compound also used in traditional Eastern medicine. However, it’s unsafe for cats and can cause vomiting, diarrhea and lethargy. The paeonol is concentrated in the bark, and while not typically fatal, it can certainly be a nuisance for both cats and their parents.  

Rhododendron

rhododendron plant

The rhododendron family includes azaleas and mountain laurels, which are harmful to cats. Rhododendrons contain grayanotoxins—toxins that affect how sodium moves within cells which can cause diarrhea, vomiting, lack of appetite, abdominal pain, changes in blood pressure and heart rate, weakness, tremors, seizures and temporary blindness. The entire plant contains grayanotoxins, but the leaves are the most toxic.   

Sago Palm

saga palm tree

Sago palms are one of the most common outdoor plants toxic to cats and dogs. The plant contains numerous toxins, including beta-methylamino-L-alanine, which is a neurotoxin, but the deadliest chemical is cycasin, which can cause liver failure in just a few days. All parts of the plant are toxic, but the seeds are the most harmful. Symptoms include vomiting, tarry stools, increased thirst, jaundice and lethargy. Sago palms can cause permanent liver damage and so immediate veterinary care is needed if ingested. 

Tulips

tulip plant

“Are tulips toxic to cats?” Their bulb-like shape and variety of stunning colors may be beautiful, but these flowers shouldn’t be kept around felines. Tulips contain tulipalin A and B—toxins that are especially concentrated in the flower bulb. In cats, they can cause vomiting, diarrhea and depression or listlessness. Call your veterinarian for advice if you notice these symptoms.  

Wisteria

wisteria tree

Wisteria contains two toxins—lectin and wisterin. Lectin is a protein that can cause digestive upset and interfere with mineral absorption, but wisterin is the worse of the two. It’s a glycoside that can cause vomiting—including bloody vomiting—diarrhea, dehydration and listlessness. The bark and flowers are poisonous, but the seeds and pods are the most toxic.  

More Plants that are Dangerous to Cats

  • Apple trees: Apple trees contain cyanogenic glycosides, which are particularly toxic when the leaves are wilting. They can cause dilated pupils, difficulty breathing, panting and even shock in dogs and cats.
  • Azaleas: Another common outdoor favorite, azaleas, contain grayantoxin, which causes diarrhea, weakness and potentially cardiac failure in dogs and cats.
  • Birds of paradise: Although beautiful, the bird of paradise (or crane flower) contains GI irritants that may cause nausea, vomiting and drowsiness in dogs and cats.
  • Boxwoods: This common outdoor bush contains alkaloids that may cause vomiting and diarrhea in dogs and cats.
  • Calla lily: This particular lily causes intense oral irritation of the mouth, tongue and lips, as well as excessive drooling, vomiting and difficulty swallowing in both dogs and cats. (It’s essential to note that the traditional lily, while nontoxic to dogs, is extremely toxic to cats and can cause kidney failure.)
  • Holly: While this plant is grown outdoors, you may also see it inside during the winter months. However, it can be harmful to your pets as the spikey leaves can cause upset in your pet’s GI tract while also introducing potentially toxic substances like saponins, methylxanthines, and cyanogens.
  • Oleanders: Popular in many areas due to their ease of cultivation, this plant has been found to be toxic to many animals. The cardiac glycosides found in oleanders can cause hyperkalemia, where your pet has potassium levels that are too high which can cause negative effects on the gastrointestinal system, blood pressure and neurological system.
  • Aloe: Aloe contains both saponins and anthraquinones, both of which have been known to cause vomiting, lethargy and diarrhea in dogs and cats.

FAQs about plants toxic to cats

What are the symptoms of plant poisoning in cats?

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Symptoms can vary depending on the type of plant, the part of the plant your pet ate and the amount ingested. Many outdoor plants toxic to cats cause gastrointestinal distress, including lack of appetite, vomiting and diarrhea. Changes in behavior—including listlessness or depression—are also red flags. Other signs to look out for include excessive drinking or urinating, drooling, difficulty breathing, twitching or seizures and collapse.   

What do I do if my cat ate a toxic plant?

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If you suspect your cat has eaten a toxic plant, consult your veterinarian or contact pet poison control immediately. Even if your cat is not showing symptoms—or they are acting strangely, but you’re not sure they ingested a plant—it’s better to be safe than sorry. If you can, bring part of the plant with you when you see your vet.  

Is water from a vase poisonous?

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The water in a vase containing the flowers of outdoor plants toxic to cats may also be dangerous. It depends on the plant involved and the amount ingested, but it’s recommended that you keep flowers away from cats or use tall vases with small openings that aren’t big enough for your cat to peek their head in and drink from the water.

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