Along the bark of each tree are thick lines of manna, a white mineral-rich resin referenced in the Bible 17 times that has been used as a natural sweetener and medicinal aid for centuries. Manna harvesting (the practice of cutting the bark of Fraxinus ornus trees to collect their sap), used to be a common practice throughout the Mediterranean. But in the past 80 years, urbanisation and industrialisation have led to it nearly vanishing.