Ontario’s flora contributes to the beauty of our natural environment and is used in food, medicine, and more. Many plants, fungi, and bacteria found in our environment are toxic to our canine friends.  Learn about some of the plants and other flora you should avoid if you have a dog, and what to do if you think your dog may have ingested a toxic plant.

Ontario plants that are toxic to dogs

If you live in Ontario and have a dog, these are some of the plants – as well as some common bacteria and fungi- you should be mindful of. These toxic flora  may be found indoors, in gardens, on the ground, or in water. Keep in mind that  even non-toxic plants may cause gastrointestinal upset or other distress when ingested in large enough amounts. However, there are a few toxic plants that can cause poisoning in your pet, even if consumed in small quantities.

To be safe, avoid letting your dog consume or chew on any plants or other debris they pick up off the ground. Similarly, don’t let them drink from potentially contaminated water sources. Leaves, seeds, and other plant material can leach toxins into water, regardless of if they drifted into a pond or you cut the stems to place blossoms in a vase. Research any plants you choose to keep around your home. Some plants, like dog-strangling vine, sound dangerous, but are harmless to dogs, while other common plants you may not suspect, such as tulips, are considered toxic. Note this is not a complete list but includes some of the more common toxic flora you may come across in Ontario.

• Yew – extremely toxic

Yew contains a toxin called taxine and should be kept away from your home if you have dogs, and avoided when on walks or hikes. Only a tiny amount of yew needs to be ingested to cause serious problems or even death, even in larger dogs. A dog may ingest a lethal amount of yew simply from playing with a stick or branch from a yew plant.

• Sago palm – extremely toxic

This plant looks like a miniature palm tree and is found both indoors and outdoors. It only takes a small amount of sago palm to poison a dog, so extra caution should be taken with this plant. Early symptoms of toxicity are vomiting and diarrhea. Damage to the liver and central nervous system can rapidly lead to death.

• Castor bean plants (also called mole bean plants or African wonder trees) – extremely toxic

This tropical plant is not native to Ontario but it is popular for decorative use in gardens. Castor beans contain the deadly poison ricin and chewing them releases it. Direct contact with ricin causes burns to the skin and delicate tissues of the mouth and throat. Other symptoms include bloody diarrhea, kidney failure, and death.

• Blue-green algae – extremely toxic

Blue-green algae isn’t algae or a plant at all; it’s actually a type of bacteria called cyanobacteria. Blue-green algae can occur in any type of water, but blooms are most common in warm, shallow, still, fresh water. Subsequently, you and your dog may come across it in lakes and ponds in Ontario during warmer months. Dogs are exposed when they ingest the bacteria while drinking, swimming, or otherwise playing in contaminated water sources. Avoid letting your dog drink water from ponds, lakes, or other stagnant water sources, and be cautious of where they swim. In large amounts, the cyanobacteria in blue-green algae can cause death in dogs, and in lower amounts, it may cause vomiting, diarrhea, and dehydration.

• Poisonous mushrooms – moderately to extremely toxic

Mushrooms aren’t plants; they’re fungi, but they also have the potential to sicken dogs. While there are plenty of mushrooms that are safe for human and animal consumption, it’s difficult to tell the difference. To be safe, avoid foraging for mushrooms with your dog and stick to safe varieties from the produce section of a grocery store. Ingestion of poisonous mushrooms can lead to altered consciousness, incoordination, liver and kidney failure, slow heart rate, and difficulty breathing, and death.

• Tulips and other flowering bulb plants – mildly toxic but physically dangerous to ingest

The toxins in tulips are found throughout the plant but are concentrated in the bulbs. Ingestion of enough of these toxins can cause vomiting and diarrhea. The symptoms may vary from mild to severe enough to warrant hospitalization for the subsequent dehydration and weakness. Eating tulip bulbs poses an additional threat because they are the right size and shape to cause intestinal blockage, which can be life-threatening.

• Lily of the valley – moderately toxic

Lily of the valley belongs to a group of plants that contain cardiac glycosides: chemicals that affect the heart. This is great if you’re in the pharmaceutical industry looking to manufacture digitalis, but not the best thing if you’re a dog consuming it indiscriminately. All parts of the plant are toxic and even small doses can be lethal. Symptoms usually start within a few hours of ingestion and include vomiting and diarrhea along with signs of shock like pale gums, weakness, collapse, loss of consciousness.

• Azaleas or rhododendrons – moderately toxic

Ingesting small amounts of azalea usually causes nothing more serious than some gastrointestinal upset that resolves itself. Consumption of larger amounts has the potential to cause more serious reactions, such as heart problems, weakness, lack of coordination, and in some instances death.

• Allium plants (chives, garlic, onion, and leeks) – moderately toxic

These edible plants are commonly grown in gardens for human consumption but they are not safe for dogs to eat. Dogs don’t share our resistance to the disulfide toxins present in allium plant species, so they can suffer red blood cell damage after consumption as a result. If your dog eats enough chives, garlic, onion, or leeks, they may lose enough red blood cells to become anemic. In severe cases, potentially lethal kidney damage can follow. In contrast to the rapid onset of symptoms associated with most types of toxic plant ingestion, it usually takes a few days for symptoms like appetite loss, lethargy, weakness, and vomiting to show up. Healthy dogs have a lot of red blood cells, so they shouldn’t suffer severe damage after eating a small amount of any type of allium plant. Consuming larger amounts in one sitting or frequent ingestion of small amounts over time is more likely to cause a significant loss of red blood cells. Japanese breeds like the Akita and Shiba Inu, may have a higher risk of developing anemia and kidney damage following ingestion of chives, garlic, onion, and leeks.

• Cannabis (also known as Marijuana) – mildly toxic

Consumption of cannabis – especially prior to processing – is not usually fatal for dogs but it can have serious and distressing effects that take a day or more to wear off. One of the reasons pet owners should be extra cautious with cannabis is that dogs tend to be attracted to the strong smell, and will commonly seek it out and ingest it, resulting in THC intoxication.

What to do if your dog eats a toxic plant

If you know your dog has ingested a toxic plant, don’t wait to get help from a veterinarian. Some symptoms of toxicity may not present immediately after consumption and can take a few hours or even days to affect your dog, and treatment is more likely to be successful the sooner it’s started. Retain the pieces of the plant for identification and call poison control or a veterinary professional immediately. Similarly, if you find that your dog is sick and notice plant matter in their vomit, save the pieces of plant matter to aid in identifying the culprit as you check around your house and garden. Correctly identifying a toxic substance that’s been ingested helps guide treatment and improves outcomes. If your dog is displaying unusual behavior and you aren’t sure of the cause, book an online virtual care appointment in Ontario.