My understanding of history is that pagans throughout Europe used evergreen branches and shrubs in their celebration of nature. Like many other customs such as those surrounding Easter the pagan customs were dragged into Christian observation.
There are all sorts of cultural traditions that have been incorporated into modern culture, religious culture included. The days of the week and names of the months, planets, major stars and constellations, for starters. The names of countries and regions and oceans and seas. People's names, in many cases.
And, of course, foodstuffs.
Cocoa was a sacred drink among the MesoAmerican god-rulers. Is it therefore pagan to drink cocoa?
When coffee drinking was introduced into Italy, a popular saying among churchmen was "Coffee is from the devil, but we have baptized it."
There was, no doubt, a Germanic tradition of the evergreen tree, which is a great symbol in the dead of the Northern European winters of something that remains green and promises the renewal of life with the spring. Baptize the notion, and put a star and an angel on the tree, and it becomes a great metaphor for Christianity itself.
There's no problem taking old pagan rites and turning them into tools of Christian learning.