The Phenomenon of Tree Suds

Photo: Suds ring on exposed tree root.

Photos and article by FMN Stephen Tzikas

Recently I noticed my Hornbeam tree was oozing suds.  These bubbles appeared near the base of the tree while it was raining.

Foamy suds at tree base.

The chemical reactions occurring in a tree that “foams” is very similar to what occurs when creating soap.  A few factors can account for this.  Sometimes tree sap can be soap-like, and hence the bubbles.  In other cases, previously settled air pollutants and plant materials interact forming a soap. These air pollutants and other nearby contaminants, might be a mix of ingredients that include salts, chemicals, and acids.  When wetted with rain water, they can combine forming rudimentary soaps.

Yet other times the foam seems to ooze from a specific spot on the trunk.  This could be an indication of a bacterial disease called slime flux or foamy canker.  If a tree had been infected, the bacteria could break down the tree tissue forming alcohol and carbon dioxide.  As the carbon dioxide escapes, it forms bubbles.

Tree suds are not restricted to Hornbeam trees.  They can form on any tree if the conditions are right.  Often oak, hickory, and poplar trees exhibit suds more frequently because of their large diameters and deep bark ridges.  These suds are harmless.