Yes, Plantain Lily is toxic to dogs!
Dogs accidentally consuming the Plantain Lily plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
Plantain Lily consumption is also toxic to Cats and Horses.
Toxic Principles Of Plantain Lily: Saponins.
More Info About The Plantain Lily Plant
Scientific Name: Hosta plantaginea
Family: Liliaceae.
Also known as: Hosta.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.