X-mas is a federal holiday in the US. Do you think that means Noahides in the US are permitted to celebrate it? Are they allowed to have X-mas trees since the intention is no longer to worship them?
Any tree (including a non-fruit tree) planted beside an idol, or beside an idol's altar or house of worship, is a forbidden decoration for the idol, and is therefore an asherah.
Likewise, trees that are brought into houses of worship to celebrate the birthday of Yeshua are forbidden as long as they remain there. In private houses or businesses, it appears that they are not forbidden for benefit if they bear no symbols of the religion, if they are only used as a custom and not as an aid in worshiping with prayers or songs. They would certainly be permitted for benefit after being discarded (a clear act of nullification) (the Divine Code by Rabbi Moshe Weiner, Ask Noah International, 2011, p 216).