Make a plan to tap red maples

According to Dr. Abby van den Berg, there are many lingering misconceptions that red maple is a “less than” species for maple syrup production. People say red maple has lower sap sugar content, that it has lower yields, that it stops running earlier and that the flavor can be “buddy,” especially late in the season.

Van den Berg is a University of Vermont research associate professor and the assistant director of the Proctor Maple Research Center. She discussed her red maple research at the 2022 Vermont Maple Conference and challenged some of the long-held assumptions sugarmakers have about red maple.

Geography is one reason van den Berg advocates for the red maple. “Red maple has a very wide range across the area of North America where we have the weather possible for maple production to happen. The native range of sugar maple is pretty limited compared to the native range of red maple, which is far reaching,” she said. Red maple is also versatile, growing in a variety of ecosystems, from swamps to high ridgetops and everything in between.

Van den Berg cited a study which estimated that there are about 530 million tappable red maple trees across the parts of North America where the weather conditions are present to produce maple syrup.

Another reason van den Berg wants producers to consider red maple is because the species adds diversity to sugarbushes. “Any element of diversity is going to help increase the resilience of our sugarbushes to various stresses or threats in the future – everything from pests to various impacts of climate change and severe weather,” she said.

To support this idea, she showed photos of a mixed stand of sugar and red maple. The sugar maple stand was nearly completely defoliated by the forest tent caterpillar, a native periodic pest in the Northeast. The red maple stand, on the other hand, was untouched by the caterpillar.

Van den Berg also thinks that red maple will prove important as sugarmakers adapt to climate change. “Red maple is predicted to fare well in response to the changing climate we’re expecting to happen as time progresses. Because it’s highly adaptable, it’s predicted to actually increase in prevalence of much of the area where we typically have maple production. Red maple is likely, in the future, to be a more important contributor to maple syrup production than it is now and ever had been,” she said.

According to van den Berg, there is no scientific research to support these negative preconceived ideas about the red maple species. With funding from a USDA Agricultural Marketing Service Acer Access grant, van den Berg implemented a study to provide empirical data to assess the lingering beliefs about red maple. The study was conducted in 2020 and 2021.

The first part of the study compared total sap yields for red maple versus sugar maple. They tapped 10 red maples and 10 sugar maples in five diameter classes. The entire system was under the same vacuum system with approximately 28 inches of mercury.  It received new check valves both years, was maintained with consistent vacuum pressure and employed modern sanitation practices.

Each of the trees in the study had its own sap collection chamber, which allowed them to quantify the amount of sap produced by each tree. They also measured the sap sugar concentration. “At the end of the season, we summed all these measurements up to get the total syrup yield produced by each tree. Then we can take the average of that to get the average total yield for each of our diameter classes,” she said.

Red maple. Photo courtesy of Paul Wray, Iowa State University, Bugwood.org

In both years of the study, the overall syrup yield of the two species was not statistically significant. In 2020, each red maple produced an average of 0.77 gallons and the sugar maples 0.72 gallons. 2021 was a poor year for sap production and the overall averages for both species was about 0.5 gallons.

By studying the daily production of both species, van den Berg also ascertained that both species followed the same flow pattern, especially toward the end of the season. She said, “There was no indication that there was any earlier cessation of sap flow with red maple compared to sugar maple when we’re looking at three in the same stand.”

The study also sought to determine if the flavor of syrup differed between the varieties. For answers, they tapped 500 sugar and red maple trees in the same stand, plumbed into separate collection systems. Once the sap was brought to the processing facility, both types were immediately concentrated to 8% sugar concentration. This was critical because using the raw sap could have resulted in different conditions in the evaporators, such as different processing lengths. The concentrated sap was boiled in identical evaporator systems – same depth, draft and draw off settings. They repeated this process four times during the 2021 season, resulting in eight samples.

According to van den Berg, the most sensitive detector of flavor is the human palate, and it is through sensory evaluations that they could do their most sensitive analysis. She said, “The first question we have to answer is is there any difference at all? Because if there isn’t any overall difference then there actually is no justification for looking how they would differ.”

Using a standard sensory evaluation test called a triangle test, 22 panelists were given three samples in opaque bottles. With each test, some tasted two red maple samples and one sugar maple sample. Others sampled two sugar maple samples and one red maple sample. They repeated this with all four samples.

One of the samples was from early in the season. Thirteen of the 22 panelists correctly identified the different sample, making it just barely statistically significant. For it to be very significant, 14 of 22 needed to get it right. Only nine out of 22 detected a difference in the late season syrup – not enough to be statistically significant.

With these data, van den Berg feels confident in going further with chemical analyses to get to the nature of the difference the panelists detected in the earlier syrup. She finds it interesting that given the perception that late season red maple syrup can have a “buddy” flavor that it was the earlier syrup where the difference was detected.

“Although we had a detectable overall difference in flavor in early season, it is likely to be rather small and pretty difficult to pick up by a general palate. There was no increased occurrence of late season off flavor,” van den Berg said. “Overall, if you have a vacuum system, there is no reason to pass by a healthy red maple with a roll of tubing.”

by Sonja Heyck-Merlin

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