Holly

When holly sprigs begin to appear on everything from picture frames to doorways and mantles, you know for sure that Christmas is coming. The placing of a ring of Holly on doors originated in Ireland as Holly was one of the main plants that flourished at Christmas time and which gave the poor ample means with which to decorate their dwellings.
Candles

Having a candle in your window on Christmas Eve meant that you were welcoming the Holy Family that found no such welcome in Bethlehem on Christmas. It may also signify that the home was one where the Catholic mass was celebrated. Either way it's a lovely tradition that exists in the US and Ireland alike.
And rest easy if your ambitious neighbor is taking down their tree on January 1. The Irish traditionally take down their decorations on Little Christmas (January 6) and it is considered to be bad luck to take them down beforehand.