Are Elm Tree poison to dogs?

I hope you are or were able to get your dog to a vet. There are many varieties of plants and I'm assuming trees as well that are very poisonous to dogs. Also, the bark could cause an obstruction if the only symptoms are vomiting, with little to no other effects. Still, your best bet is to bring your animal in to a vet, and let them know exactly what your dog ingested. They will know the right course of action to take. Best to you and your dog.