Abnormal growth on sage bush
These growth forms are akin to cancer in animals. It is not known what causes them. It could be a virus or a genetic defect. It can cause twisted growth, flattened growth (called fasciation), a proliferation of branches called witches brooms, and stem burls. Once it starts on a plant it likely will be there forever unless the plant dies or the branch dies. To get rid of it you prune out the parts with it. But if a small bit remains it can spread. There is no need to prune it out though -- it looks kind of interesting. The New York Times recently published an article on this. You can read about it on their Facebook page at https://www.facebook.com/nytimesscience/posts/896855923727768.
Amazing! Thank you so much for the reply, it's appreciated.