Sunamganj, Feb. 16 -- Every spring, a remote riverbank in northeast Bangladesh, Sunamganj, turns bright red, sparking a short-lived but major economic boost.

Along the banks of the Jadukata River in Tahirpur upazila, some 300 kilometres from Dhaka, thousands of shimul (silk cotton) trees have erupted into bloom, transforming the famed Shimul Garden into a vivid red canopy against the rolling blue hills of Meghalaya across the border.

This year's display coincided with Pahela Falgun and Valentine's Day falling on the same date, amplifying the draw. Visitors poured in from early morning, many dressed in yellow, orange and red to mark the first day of spring, turning the riverside into what locals described as a carnival of colour.

The ga...