These CA plants are harmful to humans and pets, expert says. What to look out for
AI-generated summary reviewed by our newsroom.
- Poison oak poses rising risk as heat and CO2 boost its spread and toxicity.
- Poodle-dog bush causes severe skin rashes; avoid areas recovering from fire.
- Common yard plants like lilies and tulips can cause fatal pet poisoning.
Summer in California means spending plenty of time outdoors, from beach days and backyard barbecues to sunset strolls and scenic hikes.
In 2024, California was ranked the second-best state for hiking in United States by GB The Green Brand for its stunning coastlines, dense forests and rugged mountain ranges.
Before you hit the trails or relax in your garden, it’s important to know which plants could be harmful to you or your pets.
From flowering blooms to long grasses, here are some native plants and invasive species in California that can pose a risk:
How to avoid poison oak in California
Justin Valliere, an assistant cooperative extension specialist at UC Davis who specializes in plant sciences, said there are dangerous invasive and native plant species people should look out for while outdoors in California.
“The biggest threat to folks out hiking is poison oak,” Valliere told The Modesto Bee. “It is a native plant species and does really well along trails.
He said rising temperatures, along with increased carbon dioxide levels, are contributing to the spread and increased toxicity of poison oak in California.
“This means more people may encounter poison oak and experience more severe reactions,” Valliere said.
According to the National Park Service, the main effect of poison oak on humans is an allergic reaction to urushiol, which is the oily substance found in all parts of the plant except its pollen.
This allergic reaction typically creates an itchy rash that can develop into blisters, cause discomfort and, in severe cases, might require medical attention.
“Contact with contaminated objects like clothing or pets that have touched the plant can also lead to exposure and allergic reactions,” Valliere said. “It’s best to use cold water immediately after exposure.”
Look out for these harmful native plants
Another native plant to avoid is eriodictyon parryi — or better known as poodle-dog bush, Valliere said.
It’s most commonly found in Southern California and tends to thrive in areas recovering from wildfires.
“It’s in the forget-me-not family,” Valliere said. “In that family, a lot of the plants produce fine hairs on their leaves that can cause a severe skin rash and irritation, even worse than poison oak.”
According to the National Institutes of Health, poodle-dog bush is a “growing cause of contact dermatitis in California.”
If you come into contact with poodle dog bush, the health agency said, immediately wash the affected area with soap and water to remove plant oils. Avoid touching the area and potentially spreading the oils to other parts of your body.
Antihistamines are not effective, the health agency said. Instead, use topical treatments such as calamine lotion, cold compresses and, in severe cases, corticosteroids to provide relief from the rash and itching.
Is milkweed dangerous? Poison hemlock?
According to Valliere, people and pets should avoid coming in contact with several invasive plants in California, including:
- Certain grasses, which produce long awns and seeds that can irritate skin, get stuck in pets’ fur, and cause discomfort for both animals and humans.
- Puncture vine, whose sharp seeds can pierce skin and paws, making it painful for pets.
- Poison hemlock, a highly toxic plant that can cause symptoms including vomiting, seizures and respiratory failure if ingested.
- Giant hogweed, which releases a sap that reacts with sunlight and can lead to severe skin burns.
Milkweed, which can be toxic to pets and livestock if ingested.
Gypsum weed, which contains toxic chemicals that can be dangerous to both people and animals, causing hallucinations or worse if consumed.
“The famous adage is ‘Leaves of three, leave them be,’ ” Valliere said. “Prevention is also good practice. Don’t touch plants if you don’t know what it is — and certainly, don’t eat it.”
To avoid brushing against dangerous plants, he said, wear long-sleeved shirts, pants and similar clothing when outdoors.
If a dangerous plant touches you, shower as soon as you can after the encounter.
What toxic plants should my pet avoid?
According to UC Davis, here are a few plants your pet should avoid:
- Daffodil, which can cause vomiting, diarrhea, stomach pain, irregular heartbeat and breathing problems.
- Tulip and hyacinth, which can cause drooling, vomiting, diarrhea and dehydration.
- Lilies, which can cause kidney failure within three days. Symptoms include vomiting, tiredness and loss of appetite.
- Lily of the valley, which affects the heart. Exposure can lead to vomiting, slow heart rate, irregular heartbeat and seizures.
- Crocus, which can cause vomiting, bleeding, liver and kidney damage and breathing failure.
- Chrysanthemum, which can irritate the stomach and affect the nervous system. Symptoms include vomiting, drooling and loss of coordination.
- Cyclamen, which can lead to vomiting, diarrhea and seizures.
- Rhododendron, which can cause vomiting and heart and blood pressure issues, as well as tremors, paralysis and difficulty breathing.
- Cycads, which can cause vomiting, black stool, jaundice, liver failure and death.
“If you suspect your pet has ingested any of the following plants, call your veterinarian immediately,” UC Davis said. “Do not wait to see if symptoms appear because in some cases of poisoning, by the time symptoms appear, it’s too late to save the animal.”
This story was originally published July 14, 2025 at 5:00 AM with the headline "These CA plants are harmful to humans and pets, expert says. What to look out for."
