Maple syrup comes from the sap of maple trees. In the early spring, if you cut the bark of (or drill a hole into) certain species of maple trees, clear sap will leak from the cut. This sap is very thin -- almost like water -- but it contains about 2-percent sugar (sucrose). If you boil this watery sap to drive off the water, you eventually get maple syrup. It takes 30 or 40 gallons of sap to make 1 gallon of maple pancake syrup. One tree might yield 10 gallons (38 liters) of sap over the course of four weeks.