Yes, Lily of the Palace is toxic to dogs!
Dogs accidentally consuming the Lily of the Palace 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).
Lily of the Palace consumption is also toxic to Cats.
Toxic Principles Of Lily of the Palace: Lycorine and other alkaloids.
More Info About The Lily of the Palace Plant
Scientific Name: Hippeastrum spp.
Family: Amaryllidaceae.
Also known as: Amaryllis, Fire Lily, Barbados Lily, Ridderstjerne.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.