Wednesday, May 9, 2012

Tree drool

Drool at base of white cedar tree Bubbles accumulating in groove at base of elm Drool where water landed after dripping off scar on red maple
What: The trees were drooling! I'll cover this later when I get some better photos of tree drool, but in short, the appearance of pools of white foam/bubbles at the base of trees during rainstorms is connected to stemflow (the amount of water that flows down a trees trunk, rather than falling directly to the ground). As rain washes down the surface of a tree, it picks up lots of stuff (minerals, pollen, spores, dead bug parts, etc) that dissolve into the flowing water. Somehow this decreases the surface tension of the water allowing the water to more readily bubble. I'm not so satisfied with this explanation (surprisingly little is known about tree drool) and will look into it more...

I did notice that the bubbles have an oily irridescence and seemed to pool at points where bark funneled and suddenly stopped or, as on the red maple in the photo above, where a scar or branch dripped water to a lower spot on the tree. Seemed to also be at the base of larger trees with mature bark.

Ecological notes: First soaking rain in a long while. Felt really good to be out in the woods with the fresh smell of rain washing the trees clean. The warm weather combined with the rain and everything just exploded. Things had been becoming green and now the woods has this vibrant fullness to its green.

Where: Centennial Woods

Other notes: First kingfisher in Centennial Woods in 2 years. Beavers are going to town on the hemlocks - probably not much longer for CW.


  1. Take a look at Pojasek's 1977 article: Surface microlayers and foams—source and metal transport in aquatic systems (

    It may provide some insight.