One of the prettiest fall trees in Korea is the Japanese maple, which Koreans call 단풍나무. Besides being the name for the Japanese maple, 단풍 is also a genus name for "maple trees." Actually, when Koreans refer to 단풍나무, they do not seem to be referring to any particular maple, but to maples in general, and some even seem to be using it as a general reference to "autumn leaves." I say this because Koreans describe "an excursion to view autumn leaves" as 단풍놀이. "
There are a few Japanese maples at the entrance of my school, which I noticed this morning while I was walking onto the campus. Out of curiosity, I asked the Korean gate guard what kind of trees they were. He told me they were 홍단풍나무. I checked the Forest Korea Web site, but found no such tree listed. The gate guard just seemed to be referring to the Japanese maples based on the color of their leaves. In Korean, 홍 means "red," which means it is redundant to add it to 단풍 since the "단" in 단풍 already means "red." As I mentioned above, I suspect that the gate guard may either be thinking of all maples as 단풍 or all trees with autumn colors as 단풍.
By the way, Koreans refer to a "sugar maple" as a 설탕단풍나무, and a "silver maple" as a "은단풍나무.