Whether or not a plant is poisonous to your dog depends on how much of the plant your dog ingests and absorbs. Even nonpoisonous plants can cause mild symptoms such as vomiting and diarrhea if your dog eats them. Some plants are poisonous in small doses, others only in large amounts.
In general, limit your dog’s access to any type of houseplant or ornamental plant, especially if he is prone to chewing and eating plants. If your dog has accidentally ingested a significant amount of any plant, contact your veterinarian for advice and treatment.