According to the National Christmas Tree Association, Americans bought more Christmas trees last year, and millennials are the driving force. 

The group says sales are expected to rise again this year. 

Live trees saw a 20 percent sales spike; artificial trees rose 12 percent. 

The group credits millennials starting their own families and traditions, and the growing trend of people buying more than one tree for their home. 

Some analysts believe social media savvy generations are likely to want Christmas trees because they help complete the perfect holiday photo.