Yes, Gloriosa Lily is toxic to dogs!
Dogs accidentally consuming the Gloriosa 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).
Gloriosa Lily consumption is also toxic to Cats and Horses.
Toxic Principles Of Gloriosa Lily: Colchicine related alkaloids.
More Info About The Gloriosa Lily Plant
Scientific Name: Gloriosa superba
Family: Liliaceae.
Also known as: Glory Lily, Climbing Lily, Superb Lily.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.