I ris versicolor poisoning. General poisoning notes for Iris versicolor. 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.eneral poisoning notes for Iris versicolor. 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.