Maple syrup comes from the sap of certain species of maple trees. A tap inserted into the tree trunk during sugaring season drains the sap, which is then boiled and concentrated to form the thick, sweet liquid known as maple syrup. Further boiling to evaporate the liquid results in maple sugar. Maple-flavored syrup is a mixture of a less expensive syrup, usually corn syrup, and maple syrup. Pancake syrup is artificially flavored. Once opened, maple syrup should be refrigerated.