With its green leaves and bright red and pink flowers, the eastern redbud tree (Cercis canadensis) is a visual delight. The eastern redbud’s early blooms of bright color herald the commencement of spring. But the sight of withering leaves and dying branches can cause a gardener’s heart to clench because these are the signs of canker (Botryosphaeria). The U.S. Forest Service states that canker is the “biggest problem” for the eastern redbud. If left untreated, canker can ultimately kill the affected tree. There is no chemical treatment for canker on an eastern redbud tree. But a gardener is not without hope: If caught early, canker can be stopped in its tracks by aggressive pruning, saving the tree.
Plan to prune in the early spring, before the leaf buds break open. If canker is noticed after the tree has started leafing, prune in mid-June after new leaves are fully grown. Cover the ground under the pruning area with a large tarp to catch pruned branches and leaves.
Sterilize your pruning equipment between each cut to assist in stopping any transport of canker to other parts of the tree. Mix 10 percent bleach to 90 percent water in a sterile container, such as a bucket. Dip pruning equipment in this sanitizing agent. Keep the bucket of bleach and water at the pruning site.
Locate affected areas on the eastern redbud. Examine wilting or dying branches to spot signs of canker. Canker in eastern redbud trees can be difficult to identify because the bark over the canker area often does not crack. Look for sunken areas at the base of the affected branches, where the branch joins the trunk. Use a sharp pocket knife to peel away a small segment of bark over the suspected area. The wood will be discolored to a brown or reddish-brown under the bark of the affected area.
Use sanitized garden or lopping shears to prune off dead or dying branches. Make the cut in healthy tissue, not in the canker itself. Prune the branch close to the trunk of the tree but do not cut too close to the trunk. Do not prune too far away from the trunk, leaving a stub. Sterilize pruning tools between each and every cut.
Fold the edges of your tarp to contain pruned material. Collect any other pruned branches and leaves. Dispose of them well away from the tree to avoid further contamination.
Prevent a return of canker by providing the eastern redbud tree with a healthy environment. Daniel H. Gillman, plant pathologist at University of Massachusetts, says that a healthy redbud will naturally protect itself from being affected beyond the isolated canker site. Watering, mulching, fertilizing and correct pruning will go a long way in maintaining the eastern redbud’s health.