Arthur Harris tells how the sap begins to flow every year around late January and February. Each maple tree is tapped and tubing is run to a collection tank, where a vacuum helps to draw the sap out of tree. Cold nights of 25-28 degrees contract the cells and form a vacuum.
This vacuum draws up groundwater into the tree. Every morning as the sun strikes the tree, the cells inside the tree expand and cause carbon dioxide to pressurize the tree.
The pressure results in the tree’s sap flowing.