Text byÂ CNC intern SummerÂ Hendrickson, photos by Mary Marty
The practice of collecting maple sap and turning it into maple syrup is not new. The Native Americans discovered this tree phenomenon hundreds of years ago, likely by accident. Legend tells of an Indian chief, who after removing his tomahawk from a maple tree, set out for a day of deer hunting. When his wife needed to collect water for the eveningâ€™s venison stew, she found a birch-bark bucket full of water under the maple tree. The â€˜waterâ€™ was cooked with venison from the dayâ€™s hunt, and produced the sweetest, most wonderful stew the chief had tasted. His wife had unknowingly used maple sap, which is as clear as water, and boiled it down into a sweet syrup. Maple syrup was born! Native Americans often boiled the syrup even further to create maple candy and sugar, both easier to transport than liquid.
When Europeans arrived in North America, they learned from the natives about maple sap and syruping. They experimented with collection methods, eventually drilling holes and using wooden spiles (spouts) and buckets. In the late 1800â€™s children were given a holiday from school in mid-March. This â€œsugaring offâ€ holiday was to both celebrate the sap run and to allow kids to help with the laborious process.
The tradition of March maple syrup season is still alive. Collection and processing methods have evolved, although the fundamentals prevail. Sap flow may have been mysterious to the natives and pioneers that followed, but present-day scientists have been able to provide some explanation.
To quote from the North American Maple Syrup Producers Manual, â€œThe physiology of sap flow in maple trees is a complex biological process which is not completely understood.â€ A bit of mystery still remains, allowing us to wonder at the magic of nature.
Inside a tree are several distinct layers. The phloem layer sends water and sugar, made by the leaves via photosynthesis, down to the roots for storage. In the spring the xylem layer sends water and sugar up the tree to help buds open. The xylem is also called the sapwood, and the sugar-water is known as sap. The key factor that causes sap flow is temperature fluctuation above and below freezing. Freezing nights and warmer days produce flow; maple stems are provided water, then cycle through freezing and thawing. Conflicting sources debate if root pressure is a factor.
Many of us wonder if spring sap flow is exclusive to maple trees, and if so, why? The answer to this question is a bit obscure. Trees in the maple family, and others that give off sap, have air-filled fiber cells and water-filled vessels. Species that do not ooze sap, like ash, oak, and elm trees, have water-filled fibers and gas-filled vessels.Â While birch trees exude sap in late spring, the process is not temperature dependent but based on root pressure. Birch syrup is produced in some regions of Alaska, Canada, and Russia. The ratio of birch sap to syrup is even higher than that of maple.
Sap to Syrup
Â After the right trees are drilled and outfitted with metal spiles and buckets, sap collection and processing can begin. The water-like maple sap needs to be boiled, allowing a majority of the water to evaporate off, leaving behind a concentrated sugar solution. The sap is boiled until 66.7% sugar remains. This is the legal standard for maple syrup. Syrup boils at 219Âº F, 7 degrees higher than water. This heating process imparts the darker color and flavor of maple syrup. A higher sugar percentage in the sap will result in lighter colored syrup. A lower sugar percentage in the sap will result in darker syrup, as it was boiled for a longer time. Flavor varies as well, from tree species and boiling times.
The standard ratio for determining how much sap is needed to produce how much syrup is given by 86:1. This ratio is for a 1% sugar concentration in sap. For sap with 2% sugar, the ratio becomes 86:2 or 43:1. So, with sap at 2% sugar, 43 gallons of sap is needed to produce 1 gallon of syrup. Commercial maple syrup producers generally harvest sap from sugar maples with a sap sugar concentration of 4 or 5%. At CNC, where boxelders are the primary maple specie, and production is done for educational purposes, sap sugar concentration is often 1 or 2%.
Â Getting children and adults out to learn about maple syruping has been a highlight this March. The sugar bush at CNC has been providing both sap flow and fascinating programs for over 25 years. Field trips and public programs allow visitors hands-on experience tapping trees, as well as a look at the evaporating process. Interest and curiosity trigger many common questions- some I hope can be answered by this writing.
One such inquiry is how long will it take one tree to produce enough sap for a gallon of syrup? As you may guess, the answer is not straightforward, and varies widely. However, by counting the drips of sap coming off a spile, it can roughly be determined. For example, if one spile drips 60 times a minute (this has been observed several times this season), say for 8 hours a day (only during warm hours) it would produce 28,800 drops per day. We determined the sap has a 3% sugar concentration, which takes roughly 30 gallons of sap, or 384,000 drops, to produce a gallon of syrup. In this scenario it would take over 13 days to collect 30 gallons of sap whichÂ converts toÂ one gallon of maple syrup from one tree!
Maple syruping is clearly a complicated and endlessly interesting process. I have enjoyed learning about it and teaching others. So far this season over 40 gallons of maple sap have been collected. If enough syrup is produced for educational sampling next year, CNCâ€™s maple syrup will be for sale in the Apple Shack this fall.
North American Maple Syrup Producers Manual
Wisconsin Natural Resources magazine, February 2010
Biology of Sap Flow, St. Johnâ€™s University Maple Syrup WebSite
Carpenter Nature Centerâ€™s Maple Syrup naturalist guide Â