Arbor Day is observed worldwide on March 21, with notable celebrations in Belgium, Portugal, and Lesotho. This annual holiday focuses on planting and caring for trees, coinciding with World Wood Day and the UN’s International Day of Forests. In Belgium, particularly in the Dutch-speaking region of Flanders, it is recognized as International Tree Planting Day, where tens of thousands of children and adults participate in tree planting activities, often linked to cancer awareness campaigns. Portugal celebrates Arbor Day mainly in schools, where various environment-themed activities, including tree planting, are organized; the first celebration occurred in Seixal in 1907. In Lesotho, National Tree Planting Day also takes place on March 21, although the date may vary based on the lunar cycle, with tree planting initiatives first initiated by missionaries in 1833. These observances share a common goal of promoting environmental sustainability through tree planting efforts.