which american president banned christmas trees

That would be President Calvin Coolidge, who banned Christmas trees from the White House during his presidency from 1923 to 1929. He was a conservative Republican who believed that the excessive display of Christmas trees was too extravagant and would encourage materialism and waste. Instead, he encouraged the celebration of Christmas in more modest and simple ways. Coolidge's policy was met with some controversy and criticism, but it did serve as a reminder of the importance of moderation and frugality in celebrating the holidays.