About 400 years ago in Germany, there was a custom of placing wooden girdles on the doors and ceilings of houses on New Year's Day and other festive occasions. It was also customary to hang scarecrows and lights from these wooden girders.
In this case, decorating the tree was originally a New Year's decoration. However, Christmas is December 25th, and there is only one week before New Year's. So, the custom of decorating the tree with sweets and lights became a tradition. So, it is said that Christmas decorations and New Year's decorations were somehow combined together.
For this reason, the custom of decorating Christmas trees was established in Germany about 400 years ago. Later, the German king began this custom, which was gradually imitated by others, and before long it spread throughout the world.
The Christmas tree also has a long history. If you look into the history of Christmas, you may learn many other interesting things.