Interstate 17 is a busy corridor that crosses Arizona and serves as the primary artery connecting the high-elevation mountainous regions in the north with the low-lying desert regions in the south. And for more than 35 years, an unknown group has been decorating a juniper tree between the northbound and southbound lanes, about 55 miles north of Phoenix, for the holiday season.

The juniper in question is quite isolated, surrounded only by low grasses and cacti, so it stands out from the surrounding flora. Each year, sometime before Thanksgiving, it is decorated with ribbons, tinsel, flags, ornaments, and topped with a star. A rain barrel irrigation system that helps to water the tree in the parched environment is also suspected to have been installed by the unknown decorators. The decorations are quietly removed sometime after New Year’s Day each year. Occasionally the tree is also decorated for the Fourth of July.

The tree sits on land managed by the Arizona Department of Transportation. A spokesman for the agency has indicated that they don’t know who does the annual decorating, but that since they clean up after themselves each year, they don’t interfere or investigate. Over the years wildfires have threatened the juniper but each time the tree miraculously emerges unscathed, including back in 2011 when the flames seemingly stopped right at the base of the tree itself. The tree has become a famous roadside landmark in Arizona, so much so that the official state balladeer, Dolan Ellis, wrote a song about the tree called “Scrubby.”

Update June 2022: After being badly damaged in a brush fire in 2020, the I-17 Mystery Christmas Tree died.