What is tree topping?
Mitigating the effects of inappropriate pruning with de-topping
Tree topping is a drastic pruning practice that reduces the height of trees, often used to improve views. It involves making heading cuts, often to internodes (rather than pruning to the appropriate location, close to a node). Some heavy-handed pruning styles can be appropriate and may have been used historically, such as pollarding, pleaching, and espalier. However, tree topping is never an appropriate pruning technique.
What are the results of tree topping?
Tree topping negatively affects tree health and aesthetics. The large heading cuts created during topping reduce the photosynthetic capacity of the tree, creating a stress response. In many tree species, the tree reacts by producing a large number of water sprouts at or below the heading cut. These sprouts create the aesthetically unpleasing “hydra effect” at each remaining stub.
Worse than the aesthetic result, the loss of branches and large wounds can lead to sun damage, nutrient stress, insect infestation, and decay, ultimately reducing the life span of the tree. Rapid water sprout growth, often from an internode, can result in weak attachments. Added to this, the sprouts are often growing in a decaying stub that resulted from the large tree wound. The combination of weak attachments and decay creates hazard trees.
Steps to de-top a tree
Follow these steps to restore the health and aesthetics of a tree that has been topped or suffered from breakage due to ice and wind storms:
1. Do not cause additional stress to the tree. Restoration pruning should be delayed until the tree’s remaining branches can provide substantial food to the tree. Even then, corrective pruning should be limited and occur over the course of several years.
2. Evaluate the water sprouts at each affected branch stub and hydra. Remove the smallest sprouts with the weakest connection (no more than 25% per year), and leave the larger sprouts. Late summer is the ideal time to remove water sprouts in order to reduce the number of new sprouts.
3. Choose a large sprout with the best alignment and attachment to become the main scaffold branch. Reduce the most vigorous remaining water sprouts to a strong lateral branch (see drawing).
4. Finally, remove any branch stub that remains beyond the retained water sprout to avoid decay.