Balsam Fir Motor Boat

By Jacob Rodenburg

If you have Balsam Fir near where you live, try the following activity…

Known also as the blister tree, Balsam Fir is an evergreen with relatively smooth bark.  However, scattered along the bark, at regular intervals, are elongated “blisters”; tiny pockets full of sticky balsam fir sap.  The needles of the Balsam Fir are shiny green and flat (since it’s flat you can’t roll a needle in your fingers).  From underneath, the needles are bluish-green in colour.

Take a small, sharp twig about 5 cm long and about as thick as a pencil led.  Burst one blister with your twig and make sure there is a nice globule of sap attached to the twig.  Carefully bring the twig and sap to a nearby pond (or quiet water source).  Place the twig in the water.  Watch in amazement as the twig takes off like a motorboat, making twists and turns as it zooms along the surface of the water.  The balsam sap contains an oil, which is considered hydrophobic (water hating).  As the sap makes contact with the water, it repels water molecules and as a consequence drives the twig forward.