General Poisoning Notes: Blue flag (Iris versicolor) is a native herb found in eastern and central Canada. This plant has been mentioned as causing poisoning in humans and animals, but case reports have not been found. The plant juice can cause dermatitis in sensitive individuals. glycoside, iridin (or irisin), has been implicated as the toxic compound in iris species, although this has not been confirmed (Fyles 1920, Cooper and Johnson 1984).