Prune river birch tree to one main branch, leaving two or three saplings on either side. Remove sucker shoots growing on the base of the tree to redirect nutrients to the main sapling branch. Remove the top stems, leaving one shoot leader to encourage the tree to grow upwards, and prune away all lateral branches that are twisted or fragile. To avoid infestation and disease spreading, completely cut off diseased and insect-infected branches.
Pruning early in the life of the tree is important to define the shape the tree takes as it grows. Keep lower branches to shade the trunk, but remove them as the tree grows taller to make maintenance easier. The ideal time for pruning is between late summer and early winter when sap production is lower. Sap oozing is not lethal to the health of the tree, but it is undesirable. Remove branches from the trunk or the larger branch instead of shortening the branch.
The river birch tree is susceptible to thinning due to strong winds. To avoid wind damage and increase light penetration, remove branches that grow too close to other branches or that form v-shapes.
Sanitize pruning shears or other pruning tools before and after use with a solution of one part bleach and nine parts water. Apply fungicide on fungi-infested areas, and regularly check the tree to ensure its health.