This is a list of the most dangerous houseplants and flowers which are poisonous to birds: 1. Palm trees 2. Agave or Century Plant 3. Oleander 4. Sago Palm 5. Peace Lily 6. Dieffenbachia (Dumb Cane) 7. Elephant Ear Philodendron 8. Amaryllis belladonna (Belladonna Lily) 9. Venomous Vines and Creepers