Answer: The proper time to trim your redbud tree is either immediately after it has completed blooming or when the tree is dormant in later winter (before it starts to flower or leaf out).
It is best to prune and shape this tree while it is young because of its susceptibility to so many diseases (Canker, Verticillium Wilt, and Rebud Leaf Spot, for examples). When the tree is young, the limbs or branches are small, so the wounds that are made from pruning are naturally small and will heal over quickly. In contrast, pruning off large branches results in leaving large wounds which may take several years to heal over. The longer a wound takes to heal over, the greater the risk of a pathogen entering the wound and infecting the tree with a disease.
However, if your tree is beyond the young stage, you may need to remove some large branches to achieve the desired result. In this case, remove no more than 25% of the tree's topgrowth. More than that could stress the tree and send it into decline. If more than that needs to be removed, plan to do it over a 2-3 year period. The idea of pruning is to form a tree with strong, well spaced main branches that hold true to the shape of that species of tree, along with an open, airy canopy.
Best wishes with your redbud tree!
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