December is a great time of year to prune most deciduous trees and shrubs like acers, birch and vines, whilst they are dormant. This is because the sap that they contain has dropped down to the roots and stays there until early spring. Then, come spring, it moves back up the stems to help form new leaf and flower buds.
Sap is the lifeblood of a plant. It’s filled with plant food and water and can take many forms; some is thick and gloopy, like resin found in pine trees; others free flowing like the delicious sugary syrup found in some types of maple tree.
Some trees produce a lot more sap than others, making it especially important to prune them whilst dormant to avoid profuse amounts of sap weeping out from the pruning cuts. In the case of mild winters, sap can start to rise as early as mid-February, especially in southern regions, therefore it’s important to prune during the tree’s dormancy period.