The term 'thorny tree' can be summarized by two crossword solutions: ACACIA (6 letters) and LIME (4 letters). ACACIA is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, which is native to Africa, Madagascar, and parts of Asia. It is known for its distinctive thorns and fragrant flowers. LIME is a species of small evergreen tree that is native to South and Southeast Asia. It is also known for its thorns and has been used in traditional medicine for centuries.