There are numerous plants that are poisonous to dogs. Because of this, it would be nearly impossible to go through and name each one (along with symptoms) in one brief article. Therefore, I’ve decided to split some of the mast common toxic plants to dogs into three categories: those that are mildly poisonous, moderately poisonous, and severely toxic. Plants Poisonous to Dogs with Mild Effects While many plants can result in mild toxicity, these are some of the most common: Ivy, poinsettia, tansy, nettle, wisteria (seeds/pods), and iris can all result in mild to severe digestive upset. Buttercups (Ranunculus) contain juices that can severely irritate, or even damage, a dog’s digestive system.