University of Vermont
Department of Plant and Soil Science
Dr. Leonard Perry, Horticulture Professor
University of Vermont
Many know that maple syrup comes from the sap of the sugar maple tree,
collected and boiled down each spring to make it denser. In fact,
native Americans were making it when the first European colonists
arrived. Whether you make your own maple syrup as a fun family
activity, for income, or just enjoy using it, you should know some of the
interesting facts about this important agricultural product in our region.
The Cornell University maple research and education website
(maple.dnr.cornell.edu) has many interesting facts about maple syrup,
including the one that it takes 43 gallons of sap (with 2 percent sugar
content) boiled down to make a gallon of maple syrup. Since sugar
content of the sap can vary by tree, and previous season growing conditions,
this can range from 40 to 50 gallons or more for a gallon of syrup. On
average, sugar content of sap is about 2.5 percent. If the tree is too
vigorous, it may use up more sugars and so result in less sweet sap.
Or if the tree is attacked by pests, or grows poorly, it may produce fewer
A tree in the forest with gravity lines or buckets may produce 10 to 14
gallons of sap in the spring, while roadside trees (or those in a maple
stand with vacuum tubing) may produce 15 to 20 gallons. So, in a good
season, it would take at least two roadside trees to produce enough sap for
about a gallon of syrup. The amount of sap will vary with the tree,
weather, length of the sap season, and method of collecting the sap.
The maple syrup we find in containers begins its life as sugar in the leaves
of maples, produced by the process of photosynthesis. The sugars
are transported into the wood for winter storage in the form of
carbohydrates. In spring they are converted to sucrose and dissolved
in the sap to flow through the tree.
Sugarmakers drill holes in sugar maple trees each spring, just under a half
inch wide and about two to three inches deep, at an upward angle. Bits
are inserted on which to hang buckets or similar containers (home
sugarmakers may use plastic containers), or to insert the colorful plastic
tubing one sees crisscrossing maple stands in spring.
To avoid stressing trees, only those 10 inches or more across should be
tapped. This is measured at a standard four and one half feet above
the ground (which may be seen as DBH or diameter at breast height). A tree
10 to 17 inches wide should have one tap, one 18 to 24 inches two taps, and
one larger across three taps. Proper tapping of sugar maples should
cause no injury or stress to them, and they may remain productive for 100
years or more.
With warm temperatures above freezing in spring, pressure develops in the
tree and causes the sap to flow out these openings or taps. Then, with
colder temperatures below freezing, suction within the tree pulls in more
water to make more sap. When the fluctuations in temperature lessen, the sap
stops flowing. This period of sap flow usually falls within early March to
mid April, depending on the season.
The sap is boiled to evaporate water and concentrate the sugar. The
end product will boil at about 219 degrees, seven degrees above the boiling
point of the sap. This can be checked with a candy thermometer.
The top quality syrup will contain no less than 66 percent sugar (measured
When buying maple syrup you will be confronted with some choices in grades,
all based on U.S.D.A color standards but with words that may vary with
region. Generally the darker amber the color, the stronger the maple
flavor. Make sure when buying maple syrup to read the label to make
sure it is pure, if that is what you are seeking, and of the flavor you
desire. Contrary to some claims you may hear about better syrup from one
region or state, quality of syrup will be affected instead by the season’s
weather, time of season the sap is collected, and how it is processed.
What may vary with the location or “provenance” are the many other flavor
components in maple syrup. Around 300 different compounds have been
identified, not all being present in the same syrup. In addition to
the maple flavor in all syrups, there may be caramel, vanilla, nutty,
buttery, honey, chocolate, or coffee flavors detectable.
Why the sugar maple has sweeter sap with better flavor than other maples is
not really known. The reason may lie in the structure of the wood
where the sap is stored. If sap is collected once buds develop on the
trees, it becomes less pleasing. The sugar maple has the longest
period before buds develop, so the longest season to collect sap among the
The sugar maple primarily grows in the northeastern United States and
eastern Canada, so this is where maple syrup is produced. A less sweet
syrup with different flavor is made in Alaska and Siberia from the sap of
birch trees. Another species of maple is tapped in Korea, but only to
drink the sap.
Once you have maple syrup in a properly filled and sealed container, it can
last up to a year, or up to six months in the refrigerator if opened.
When cooking, use maple sugar similar to white sugar. There is no
evidence it is healthier except that, being unrefined, it may contain
compounds with some health benefits. If using maple syrup in cooking,
you can use one cup instead of one cup white sugar. Reduce the liquid
in recipes, though, by 3 Tablespoons for each cup of syrup used.
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