Where does tree sap come from in sugar maples? Why are leaves harmful to trees in winter?
Where Does Tree Sap Come From in Sugar Maples
Tree sap is sort of like blood in animals. Most plants have sap of one sort or another, called phloem, that transports sugary substances (carbohydrates) from the cells that make it, to the cells that need to use it as energy for the business of living and growing. It travels through the plant in phloem vessels. In the spring, the phloem, which has spent the winter stored in the roots, starts traveling back up the tree to fuel the awakening buds. Humans tap some of that phloem, let it drip out into buckets, then cook it down and eat it in the form of maple sugar or syrup.
Leaves are not harmful, they are simply superfluous. In order to prepare for the cold of winter, most plant, trees included, go into a state of dormancy. Some of them (evergreen trees) do it by closing stomata and changing cell structure to produce a sort of natural antifreeze. In addition, deciduous trees get rid of their leaves, so they have much less surface to protect.