O Tannenbaum

I have an old songbook from my grandmother and it is printed "treu"

Dragging up an old thread to add another data point. I asked my grandparents about this song. They grew up in Germany in the 1920s and 30s, and subsequently left Germany, preserving, they say, their 1930s German. When asked to sing the song, they both sang the "wie gruen" version. I asked about "wie treu", and my grandmother said she had heard that version and she thinks it's an alternative version that sounds a bit stilted.