If you think weddings are a lot of work, try walking a couple of trees down the aisle. Every spring, Accettura, a mountain village of about 2,000 people in the Basilicata region of southern Italy, celebrates its patron, Saint Julian, with an arboreal wedding. Called Il Maggio di Accettura, the wedding is an ancient pagan tradition that draws thousands. Three years ago, Gianluca De Bartolo traveled to there to document it.

“For me, it has been very important to share this unique rite that has been handed down for centuries,” Mr. De Bartolo said. “It has preserved, in those centuries, peculiarities and traditions without the constraints of modern times.” Mr. De Bartolo said that the celebration is important for reuniting people who grew up in the village. In recent years, a poor economy and bleak employment outlook have forced many young people to leave Accettura. While foreign investment remains prevalent in Italy’s north, the south lags behind.