Maple syrup is a syrup usually made from the xylem sap of sugar maple, red maple, or black maple trees, although it can also be made from other maple species. In cold climates, these trees store starch in their trunks and roots before the winter; the starch is then converted to sugar that rises in the sap in late winter and early spring. Maple trees are tapped by drilling holes into their trunks and collecting the exuded sap, which is processed by heating to evaporate much of the water, leaving the concentrated syrup. It was first collected and used by the indigenous peoples of North America, and the practice was adopted by European settlers, who gradually refined production methods. Maple products are frequently sold in tourist shops and airports as souvenirs from Canada and in particular Quebec, which is far the largest producer, responsible for 70% of the world's output. The sugar maple's leaf has come to symbolize Canada, and is depicted on the country's flag. 聼起來自然嗎?