The history of upside down Christmas trees goes as far back as the middle ages, when residents of Europe hung their xmas trees upside down as a representation of the holy trinity. Of course, that is not the most common method of displaying today's Christmas tree, as what it now represents, right side up, is the tip of the tree pointing to heaven. Because of this modern attitude and style, there are those that think an upside down Christmas tree could be a sacrilege or at least a sign of disrespect.
Though there is no clear history of upside down Christmas trees we do know some of how it came about.
During 600 AD a British monk traveled to Germany to preach the word of God. He spent a lot of time in Thuringia, an area destined to become the home of the first secular xmas decorations. Here the monk, according to upside down Christmas tree history, decided to make the triangular shape a representation of the Holy Trinity made up of God the father, God the Son and God the Holy Ghost.
The Europeans he converted started to revere the monk's upside down Christmas tree, so history tells us, as the Tree of God. By the 1100's the upside down tree was appearing hanging from nearly every central European ceiling.
The first decorated Christmas tree appeared in 1510 in Latvia. A little later in that century history tells us that Martin Luther decorated a Christmas tree with candles as a way of explaining to his children how the stars shone in the night sky.
Gaily-decorated Christmas trees, not yet upside down, were first documented in Strasbourg Germany in 1601. The decorations were barley sugar twists, wafers and multi-colored flowers.