Rhododendrons are mainly concentrated in Asia, because when the ice age glaciers invaded the continents of Europe and America, they largely spared Asia, where they did not push so far south.
杜鵑多集結亞洲，因為大自然的冰河作用侵襲歐洲、美洲時，卻對亞洲留了一手，並未往南大力推進。