Many plants share a common name or cultivar name, lucifer plants among them. Two cultivars that are known as Lucifers are the montbretia (Crocosmia "Lucifer") and the cardinal flower (Lobelia cardinalis "Lucifer"). Whether or not your Lucifer plant is poisonous and a danger to Prince depends on which Lucifer cultivar you've planted.
While the montbretia cultivar "Lucifer" is not specifically listed as poisonous by the ASPCA, it is a member of the iris family (Iridaceae). Other members of the iris family may cause serious reactions if your puppy eats the corms, or bulbs, including diarrhea, excessive slobbering, stomach pain and vomiting. Keep the corms out of Prince's reach and call the veterinarian immediately if he eats your monbretia plant.
Lobelia Cardinalis Lucifer
The cardinal flower grows in moist environments, making it ideal for bog gardens and ponds. The bright red color of cardinal flowers, including the cultivar "Lucifer," attracts hummingbirds and butterflies. All parts of cardinal flowers are poisonous to humans, horses, cats and dogs. If Prince eats the leaves, stems or flowers, he may show symptoms of lobeline poisoning, including confusion, depression, slobbering, irregular heartbeat, stomach pain and vomiting. Take him to the veterinarian immediately along with a sample of the plant.