Are cottonwood trees poisonous to horses?

Cottonwood trees (Populus deltoides) are not poisonous to horses. In fact, they are a common source of food for horses in the wild. The leaves, bark, and twigs of cottonwood trees are all safe for horses to eat. However, it is important to note that cottonwood trees can be a source of respiratory problems for horses if they are exposed to the pollen. If your horse has any respiratory problems, you should avoid exposing them to cottonwood trees.