Soapy, Sappy Pine Tree
On Valentine’s Day, Sunshine sent a photo of foam at the base of a pine tree. Along with the photo, she asked a very logical question… “What is this and what caused it?” (See photo accompanying today’s post to see the bubbles in question)
It is a conundrum. A foamy, sudsy froth coming from a pine tree is an odd thing to find while out on a walk in the forest. In fact, it isn’t something many people I know have seen; even those who have spent a lot of time working, playing or walking in the piney woods. As has become the case with our discussions here, we’re going to look deeper into the science behind the mystery. What would cause this to occur at the base of a pine tree?
When I saw the photo, one of the first things I knew immediately was that there had been a great deal of rain there for an extended period of time. The reaction that occurs to make the observed foam is an extremely simple type of weak saponification, or soap-making. And this reaction only occurs during times of abundant rain.
What does rain have to do with it? The extra moisture reacts with chemicals in the pine resin, as well as chemicals in the air, to create soap-like suds. Some of the same chemicals in pine resin that contribute to the old recipes for pine tar soap are at play here. Along with phosphates and other chemicals in the air that find themselves trapped in the layers of bark on the tree, the rain (in both the form that falls on the tree and the water that has been taken up by the tree) reacts to make the bubbles.
Why does this almost always occur at (or near) the base of pine trees? That’s an easy one… Gravity! As the rain on the outside of the tree trickles and runs down the trunk of the tree, weaving its way through the bark and along the crevices of the tree, it helps froth the simple soapy substance. And, as you’d expect, this occurs more prominently as it picks up momentum and nears the base of the tree.
The joys of a rainy day walk in the woods bring far more than just tranquility on a quiet day in nature. Those walks also bring observations that pique our curiosity and opportunities to learn what causes things rarely seen in the forest. Like, the mystery of the bubbly bark! (or, the percolating pine… or, the sudsy sap… I’ll see myself out, now!) 😂