When I lived in LaPointe, Wisconsin, local tradition dictated that Christmas trees (but only the real ones) were taken down no later than New Years Day.
La Pointe is located on an Island on Lake Superior, and is accessed in winter via a three mile long ice road connecting it to the mainland.
Nighttime visibility on the ice road is nonexistent, so the town marks the road with used Christmas trees every 100 yards. Residents dump their used trees at the fire hall in early January, and the town maintenance crew sets the trees when the ice road forms soon after.