During the cold Vermont winter the sugar maple tree stores much of its sap underground below the frost line. This prevents potential cracking of the tree's "sap vessels" in the branches above ground during freezing weather. The sap begins flowing upward in the Spring and that's when we "tap" the sap and begin to boil it down.
It takes 36-40 gallons of sap to make one gallon of maple syrup which is three times as sweet as regular table sugar. The American Indian taught the colonists the art of tapping trees to make "sweet water" which rose in value when the colonialists passed an imported sugar tarrif in the 1700's. Maple syrup is a major product in Vermont’s economy.