Tree shears
Trees are commonly trimmed or pruned for appearance or for the overall health of the tree. Sap commonly rises into trees during months when the temperature falls near or below freezing.
Explanation
Maple tree tap
According to the Massachusetts Maple Producers Association, sap flows out of a tree when the internal pressure is greater than the atmospheric pressure. Sap moves both horizontally and vertically throughout the tree.
Considerations
Close-up view of sap
Trimming when the sap is flowing or rising will not necessarily damage the tree; however it is considered more of a cosmetic issue since the tree will "bleed" sap, and may look unattractive.
Time Frame
Flowering trees should be trimmed about three weeks after they have finished blooming to ensure flowers the following year.
Warnings
Example of the swollen tree collar
Trim trees only near the swollen collar, where the trunk intersects with the branch. Cut just above the collar, without cutting into the swollen area.
Expert Insight
TreeBoss.net suggests trimming or pruning trees during the middle of winter when the tree is completely dormant or when the tree is in full leaf bloom.
Tags: trees during, when tree