Birch Spike is a term used to describe a type of tree. It is composed of three different trees: CATKIN (6 letters), Tree (4 letters), and ALDER (5 letters). CATKIN is a type of small, cylindrical flower cluster found on many trees and shrubs. Tree is a perennial woody plant with a single main stem or trunk. ALDER is a genus of flowering plants in the birch family. Together, these three trees form the Birch Spike.