Is Watercress Fern toxic to cats?

Mildly. The ASPCA lists watercress fern as mildly toxic to cats — a chewing cat typically gets mouth irritation, drooling, and vomiting rather than a medical emergency, but it is still best kept out of reach. Blechnum penna-marina is not individually listed on the ASPCA Toxic and Non-Toxic Plants database, and the genus Blechnum is not covered, so a safe label cannot be asserted. True ferns are generally low-risk, but treat with caution: discourage chewing and consult a vet if a pet ingests it, as it may cause mild digestive upset.

Blechnum penna-marina is not individually listed on the ASPCA Toxic and Non-Toxic Plants database, and the genus Blechnum is not covered, so a safe label cannot be asserted. True ferns are generally low-risk, but treat with caution: discourage chewing and consult a vet if a pet ingests it, as it may cause mild digestive upset. Signs usually appear soon after chewing rather than hours later — watch for drooling, pawing at the mouth, vomiting, loss of appetite, or unusual lethargy after your cat has had access to watercress fern.

Stay calm. Remove any plant from your cat's mouth and take the plant away. Note how much was eaten and when, and do not induce vomiting unless told to. Call your vet or the ASPCA Animal Poison Control Center on (888) 426-4435 and follow their advice; a leaf or photo helps the vet treat it correctly.

The ASPCA classification Growli uses applies to both cats and dogs: Watercress Fern is mildly toxic to dogs as well. See the full watercress fern pet-safety guide for both species.

For a similar look without the risk, see the best cats-safe plants list — every plant there is ASPCA non-toxic to cats and dogs.