Out Of One's Tree Meaning

(idiomatic) Crazy; unhinged; irrational.

Example: 2003, Diane Chamberlain, Kiss River, Mira (2003), ISBN 9780778312857, page 79:
  Clay had learned to bring a book with him when he took Henry shopping; otherwise, he would go out of his tree with boredom.
2009, Terry Stocker, The Paleolithic Paradigm, AuthorHouse (2009), ISBN 9781449022938, page 324:
  I, again jokingly finalized: that to believe her own hypothesis, she had to be out of her tree, […]
2010, Helen Simpson, In-Flight Entertainment: Stories, Knopf (2010), ISBN 9780307957634, unnumbered page:
  He was singing and sobbing and carrying on, out of his tree with alcohol, […]
For more examples of usage of this term, see Citations:out of one's tree.