Saturday, April 22, 2017 1:00 am
Sap bleed OK after spring pruning
Question: I pruned my birch tree recently, and now water/sap is running down from where I made a cut on a larger branch. Will the tree die? What can I do to save it?
Answer: Your birch tree belongs to a group of trees that are referred to as “bleeder trees.”
Every spring, trees begin to move stored reserves in the roots and stems to the buds and developing leaves. The transportation system used for this movement is called the xylem. The xylem is located just underneath the bark of the tree. Think of the xylem as interconnected straws in the tree that reach from the roots to the leaves at the top of the tree.
Wind moving over tiny pores in the stems and leaves creates enough suction to draw sap from the roots to the leaves. The properties of water also help the sap “stick together” so the stream of water never “breaks.” It's an amazing process when one thinks about how far sap is drawn up through a tree.
Some trees run sap later in the spring or for longer periods. Some trees seal off cut wounds more quickly than other trees. This is why some trees such as maple and birch bleed sap more than other trees when pruned in the early spring.
As far as experts can tell, the bleeding doesn't really harm the tree. Even though the sap run can be messy, the tree will not die. So, to “stop the bleeding,” it's better to prune bleeder trees later in the spring.
Sometimes, bleeding sap can indicate a problem with some trees. Cherry and plum trees can bleed sap from the trunk and branches, indicating a disease called gummosis. Gummosis can be bacterial or fungal and can weaken the trees over time. Fungicide applications such as liquid lime sulfur or copper-based fungicides can help.
If one observes white sap bleeding from the main trunk of a pine or spruce tree, this usually spells trouble.
Bark beetles are very small beetles that can attack pines and kill them over time. Zimmerman pine moth is a devastating pest of pines. The beetle attacks where a branch meets the main trunk. Large “popcorn” masses of sap are produced where the insect attacks. Consult with a certified arborist so he or she can spray the tree two to three times a year.
White sap on the main trunks of spruce could mean the tree has a disease called cytospora canker. This disease is usually fatal, but one can have the tree sprayed and fertilized by an arborist to prolong its life.
Sometimes, sap production from a tree can be a result of pruning or injury, and it is usually not a big deal. In certain instances, sap production can be a symptom of an insect or disease problem.
The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery is the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.