05/16/2023
A couple of weeks ago, amidst all of the rain, you may have seen some trees seemingly blowing bubbles! This is caused by stemflow.
Stemflow is the act of water flowing down a plant’s trunk or stem. During dry periods, things like particulates, plant chemicals, and air pollutants build on the bark surface of trees. When rain collects on a tree’s canopy and subsequently flows down the tree, these ingredients mix and concentrate towards the base of the tree. The foam is actually the result of a sort of crude soap, foaming because of the turbulence on tree bark furrows. Soap is a combination of an alkali metal (like sodium or potassium) and a mixture of carboxylic acids.
The best time to see these suds is during an extended rainfall following several weeks without rain. The deeper the ridges of the tree and the greater the diameter, the more likely you’ll see them, since surface area is increased.
