The term 'Birch Tree Relative' can be summarized by the crossword solution 'ALDER, ' which is a five-letter word. ALDER is a type of tree that is related to the birch tree and is found in many parts of the world. It is a deciduous tree that grows in wet areas, such as near rivers and streams, and is known for its fast growth rate. ALDER wood is often used for furniture, flooring, and other woodworking projects.