Toxic plants

Is Klamath Weed or St. John’s Wort Toxic To Cats?

Is Klamath Weed or St. John’s Wort Toxic To Cats? 
Written by Clair Chesterman

Klamath weed or also commonly known as St. John’s Wort is a flowering plant that is found to contain hypericin. Hypericin causes photosensitivity, increased heart rate, and skin ulcers when ingested by cats. Photosensitivity puts your cat at risk for sunburns, blisters, and skin cancer. While Klamath weed poisoning is rarely fatal, it is still vital to get your cat to a veterinarian for appropriate treatment.

What Is Klamath Weed or St. John’s Wort?

Klamath weed is native to temperate Eurasia and has spread as an invasive species throughout North and South America, and also in South Africa and Australia. This plant from the Clusiaceae family has long been used in traditional medicine and is still commercially grown in the twenty-first century.

The rhizomes of Klamath weed are extensive and creeping, and the stems are reddish. This invasive plant can reach a height of three feet. It has opposite and stalkless leaves that are narrow, oblong-shaped, and yellow-green in color, with scattered translucent dots of glandular tissue. Its branches are typically clustered around a depressed base, and it has opposite and stalkless leaves that are narrow, oblong-shaped, and yellow-green in color. The flowers are bright yellow with prominent black spots and have five petals and sepals.

Clinical Signs of Klamath Weed or St. John’s Wort Poisoning in Cats

Cats may experience a variety of symptoms of Klamath weed poisoning. Some cats may not show any harmful side effects after ingesting Klamath weed, while others cats may manifest the following clinical signs:

  • Photosensitization
  • Ulcers on the skin
  • Blisters
  • Increased temperature and heart rate
  • Dermatitis

First Aid and Treatment of Klamath Weed or St. John’s Wort Poisoning in Cats

The usual treatment for plant poisoning will be also done to cure your cat of Klamath weed poisoning. The veterinarian’s treatment may include administering activated charcoal, inducing vomit, intravenous fluid therapy, and performing gastric lavage. These procedures may be done depending on the veterinarian’s discretion. 

If your cat’s skin has developed blisters or ulcers, the doctor will usually use topical treatments to ease itching and minimize swelling. In extreme circumstances, oral corticosteroids may be used.

Recovery from Klamath Weed or St. John’s Wort Poisoning in Cats

Klamath weed toxicity in cats is virtually always benign. Most cats will be returned to their owners after treatment, but if the cat is severely dehydrated as a result of the treatment, he may need to be watched at the veterinarian’s office.

Prevention of Klamath Weed or St. John’s Wort Poisoning in Cats

If Klamath weeds are present in your yards, remove them right away. Indoors is the safest place for your cats as you can keep an eye on them. To keep them indoors, engage them, and keep them mentally stimulated to prevent them from getting bored and start wandering away. Try planting cat-friendly plants as an alternative.

If you love plants but have cats at home, check out these lists:

About the author

Clair Chesterman

Clair Chesterman is a professional cat breeder having her own cageless CFA and CCA Registered cattery & fostering company FluffyMeowPaws in Eugene, Oregon. Clair is a plant enthusiast too and she made in-depth research on toxic and non-toxic plants for cats.

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