Tag Archives: shade tolerance

Maple syrup mechanics: xylem, sap flow, and sugar content

It’s maple syrup making time in the Northeast.  Jeanne explains the mechanics of sap flow, collecting sap for syrup making, and why maples are special in this regard.  

Proctor maple research field station, Underhill, VT

Proctor maple research field station, Underhill, VT

I had the great pleasure last weekend to visit the University of Vermont’s Proctor Maple Research Center in Underhill, VT, where the sugar maple (Acer saccharum, Sapindaceae) sap is flowing.  Sugar maple trees all around the northern hardwood forests in the Midwestern and Northeastern United States and southeastern Canada can now be “tapped,” fitted with a hollow tube in the sapwood, out of which sap flows and is collected and boiled down to maple syrup.

Tapping sugar maple to collect sap

Tapping sugar maple to collect sap, Proctor research station, Underhill, VT.

Maple syrup might be the oldest agricultural product in North America. Early 17th-century written records from Europeans exploring North America describe Native American use of sugar maple sap.  We of course can’t know how Native Americans discovered sugar maple sap, but it may have been by sampling a “sapsicle,” icicles made from frozen maple sap that forms at the end of a broken twig.  The evaporation of water during ice crystallization partially concentrates the sugar in the sap, making the sapsicle particularly sweet.  To understand how that sap got to the end of the twig in the dead of winter and why it’s so sweet, we need some basics about plant vasculature and carbohydrate storage and must figure out what makes maples so special. Continue reading