Hostas, also called plantain lilies, are poisonous to dogs. Toxic effects occur when a dog chews or ingests the leaves, roots and flowers of the hosta.
Hostas contain saponin, a material that foams up when combined with moisture in the dog's digestive tract. This foam can potentially paralyze the digestive tract and can cause bloating or twisting of the stomach or intestines. A dog who ingests hosta is likely to have severe stomach pain with eventual diarrhea and vomiting. Ingestion of hosta is rarely fatal but can cause a dog to feel uncomfortable and depressed. The severity of symptoms is directly related to the size of the dog and the amount of saponin ingested.