Foaming or drooling trees is the latest thing that can be blamed on recent heavy rains around the state. The downpours have made some trunks look a bit like a messy soap dispenser.
In some spots, the foamy discharge is heavy enough it gathers around the base of the trees like a large, soapy puddle.
As odd as it may look, it’s perfectly natural and nothing to worry about, according to tree experts. The foamy liquid is part of what tree scientists refer to as stemflow, and it goes on all the time but under certain conditions it can become quite foamy and visible.
Stemflow is the term used to describe the basic act of water flowing down the exterior of a tree or plant.
“Plants and trees produce all kinds of different chemicals they use in the biological process of being alive,” said Jay Wasan, assistant professor of forest ecosystem physiology at the University of Maine. “Certain ones have waste products that are distributed to the [outer] bark of the tree.”
In dry conditions, those chemical deposits build up in the nooks and crannies of the tree trunk’s bark. The chemicals include acids, salts and other organic compounds — ingredients used in soap making.
If the dry conditions last long enough, a good rain will mix those chemicals together and create a sort of natural tree soap. As the tree soap flows down the trunk of the tree, the uneven surface on the bark agitates it enough to create bubbles or foam.
“The rain is washing off that layer of residue the tree produces,” Wason said. “Plants are also producing pollen [and] this is an active time of year with a lot of metabolic things going on inside the trees.”
Which means trees in parts of Maine are ripe for soap production.
The phenomena seems to be more common in trees that produce compounds that smell nice, according to Wason.
“We can all imagine the nice smell of a pine tree or a fir tree,” he said. “But there is not much smell from a birch.”
The soap-like liquid does not harm the tree and is not dangerous to birds, animals or other plants.
And even though it is a watery mixture, Wason said it is not safe to drink as it likely contains high amounts of salts and magnesium. There could also be pollution particulates trapped in the soap.
“It can really be something to see,” he said. “I have walked into the woods and seen it at times where it looks like someone had washed the trees and it looks like a big pile of soap suds at the base of the trees.”