Want to know something sweet? Acer saccharum, commonly known as the sugar maple tree, has been a natural resource for maple syrup for many centuries. This hardwood deciduous tree is native to the Northeastern United States and Eastern Canada, and is especially important to the history, culture, economy, and foliage of these regions.
Sugar maples can reach up to 30 m/100 feet high and collectively grow on approximately 31 million acres of land. Many mammals and insects use the sugar maple as a source of food, while woodpeckers and other birds nest in its branches. The leaves of a maple tree have five lobes and turn brilliant shades of yellow to red in the fall.
Sugar Maple leaves. Credit: Superior National Forest. CC BY 2.0
The Latin name Acer saccharum means “sharp sugar.” The “sharp” genus name refers to the shapes of the leaves, which have numerous, pointed tips. The “sugar” species name, of course, is a tribute to the tree’s sweet, delicious maple syrup product, made by refining its sap. The high sugar content of the sugar maple’s sap has made it into a unique resource in North America for centuries.
The sugar maple is known by other names. It can sometimes be called the "rock maple" or the "hard maple" as maple trees also produce some of the densest and hardest wood known. As well as producing syrup, they are an important source as firewood, lumber, and pulpwood for paper production.
A Sweet History
Native Americans processed sugar maple sap long before Europeans arrived in the northeast region of the United States. They made maple candies, maple drinks, and used maple syrup as a cooking ingredient. Myths and legends about maple trees and syrup were widespread among the tribes. It is unknown whether Native Americans or European settlers were the first to boil sugar maple sap, but both were using the process by the eighteenth century. French explorers and fur trappers who came to North America traded for these maple syrup products. In the late eighteenth and early nineteenth centuries, some people, including Thomas Jefferson, thought that maple sugar could become an alternative to cane sugar. Indeed, Jefferson had his own maple plantation at Monticello. However, processing maple sap is extremely labor-intensive, and thus, far more expensive to produce.
Maple sap buckets. Credit: Dave Pape. Public Domain
Sap processing has not changed much over the centuries. Improvements in technology have made boiling sap more efficient, but it still takes 40 or more gallons of boiled-down maple sap to make one gallon of maple syrup. A single tree can produce about 20 gallons of sap in the short season for maple sugaring. “Tapping” the trees occurs in spring when nights are below freezing and daytime sunshine brings the temperatures above freezing. This creates a unique thawing and freezing cycles that increase pressure inside the tree’s vasculature and force sap out of the tap.
Did you know? The process of tapping sap from trees does not harm maples. Even when using a vacuum-tubing system to increase the amount of sap exiting the tree, maple-sugaring takes only a fraction of the tree’s available carbohydrates.
A Changing Climate
Sugar maple. Credit: Bruce Marlin. CC BY-SA 2.5
Eastern North American sugar maples support a multibillion-dollar syrup industry. Climate change threatens to severely impact the growth of sugar maples in New England, which depend on the region’s springtime cycles of freezing nights and mild, sunny days for sugar-producing processes. Warmer weather stresses the trees and the months in which tapping occurs in more Southern states, such as Virginia, has already shifted because of seasonal climate changes. Increases in New England’s temperatures will push maple sugar growth further north, into Canada. Because the trees depend on unique springtime fluctuations in temperature from day to night, shorter winters are disruptive for the maple sugaring season.
Studies by scientists from the Harvard Forest in Petersham, Massachusetts, suggest that in the last few decades, some maple sugar trees have been exhibiting reduced productivity and growth. The stressors and causes for maple decline are not precisely clear, but include acid deposition in soils from rains and climate change. This is a major concern for sugar maples and the organisms that depend on this keystone species.
Did you know? Sugarers know to stop tapping their trees when the buds of maple trees “break,” giving rise to spring’s new leaves. At this time, the syrup produced will have a funny taste, and most of the sap will be recruited to the leaves so that the water and sugar can be used in biological processes.
A comprehensive subject guide on the sugar maple and maple syrup from the University of Vermont
Information on the study of sugar maples from the Harvard Forest