Research: Syrup Producing Syrup from Black Walnut in the Eastern Michael Farrell, Director, The Uihlein Forest, Cornell University Ken Mudge, Associate Professor of Horticulture, Cornell University

hough it is not well known, all reported in North America in the 19th species of walnut (Juglans spp.) century as part of a comprehensive Tproduce a sweet that can be study of sap flow in plants (Clark 1874). boiled down into valuable syrup. There Sap flow in English walnut (Juglans re- is a well-established resource of black gia) has also been studied in due walnut () trees throughout to the worldwide importance of eastern North America that could be production in this species (Ewers et al. utilized for syrup production to com- 2001). Controlled research in an Eng- plement existing sugaring operations. lish walnut and greenhouse However, very little information exists demonstrated the capacity of autumn, on the optimum tapping time for these winter, and spring sap flows through a species, the expected yields from tradi- combination of stem and pressures. tional bucket or more modern vacuum- The researchers never investigated the enhanced tubing systems, and the over- potential to use this sap as a source of all economic outlook for producing syrup production and there is no such walnut syrup. Although many sugar- data on potential sap yields and sugar makers are interested in tapping these content for tapping black walnut in the trees to complement existing sugaring United States. operations, better data is needed on po- The only research on using the sap of tential yields and market opportunities black walnut trees for syrup production before investing in planting these trees took place in Kansas nearly a decade or seeking out existing trees to tap. ago (Naughton et al. 2006). It was limit- Although the number of tappable ed in nature and meant as a preliminary black is significantly less than study. Despite the promising results, the number of tappable maples (Farrell no follow-up studies were conducted. 2013), there are excellent opportunities Todd Leuty from the Ontario Minis- for sugarmakers to utilize the trees they try of Agriculture recently conducted currently have while also planting these research on tapping Japanese walnuts trees for long-term benefits. They grow grafted onto black walnut rootstock in extremely fast and are relatively easy Ontario. His findings, as well as other to establish in open fields and along practical experience, indicates that the watercourses as riparian buffers. Most sugar content of walnuts mirrors that of people currently plant walnut trees for maples, yet the amount of sap flow is their timber value and nut production. significantly less. Whether the amount If it is also economically viable to tap of sap produced is so low that it limits them for syrup production, this could the commercial potential of this species result in many more trees being estab- is not yet known. Furthermore, none of lished throughout the Northeast. the previous studies were done with

Sap flow in walnut trees was first Walnut: continued on page 34

December 2014 33 Walnut: continued from page 33 duced, following the rule of 87.1. high-vacuum tubing and there isn’t yet Results any reliable data on what one can ex- pect from tapping black walnuts. Since Figure 1 shows the running total of vacuum tubing can produce two to ounces of syrup produced per tap at three times the amount of sap as grav- the four locations. The highest yielding ity flow in maples, it is important to site (Erie PA) produced an equivalent of determine the effect of vacuum assisted 11 ounces of syrup per tap whereas the sap flow on walnuts. This article will lowest performer (Syracuse) yielded address preliminary research exploring only 6 ounces of syrup per tap. Figure the potential yields from black walnut 2 displays the total sap production per trees in the eastern U.S. tap during each collection at the four sites. These should not be considered Methods daily totals, since sap was not collected on every day that it ran, but rather at In order to determine potential longer intervals due to labor restric- yields from black walnuts, we collected tions and the low volumes of sap flow. sap at four sites in New York, Pennsyl- Figure 3 displays the average sugar vania, and Indiana during the winter of content during each collection at the 2014. In New York, we tapped 58 trees four locations. In a similar manner to using individual bags and 5/16 spouts maple sap flow, sap sugar content was on Cornell’s campus in Ithaca and 96 very low in the fall (less than 1%) and trees using vacuum tubing at Lemoyne much higher in the spring (2-3.5%). College in Syracuse with the assistance Although not shown in Figure 3 since of Kris Dulmer and Steve Cacccamo. A it only displays the average sap sugar sap puller diaphragm vacuum pump concentrations, the highest reading tak- was utilized at this site with an average en was 6.2% and there were many trees reading at the pump of 18” Hg. Jacob producing sap in the 4-5% sap sugar Noonan served as a research collabora- concentration range. tor and tapped 35 trees on buckets with 5/16 spouts in Erie, PA. Rich Hines also Discussion tapped 10 trees with 7/16 spouts and buckets in Indiana. Whereas the trees at Although the sap yields observed most sites were tapped in mid-Febru- in this study were extremely low when ary, Hines tapped his trees on Novem- compared to traditional ber 19 to explore the possibility of sap production, it is important to realize flow in autumn. At all locations, every time sap was collected (usu- ally every 4-7 days), the total volume and sugar content of the sap was measured and recorded. At the end of the season, all of the data was analyzed and normalized to equate Figure 1. Running total of walnut syrup production (oz/tap) to ounces of syrup pro- at four locations during the 2014 sugaring season

34 Maple Syrup Digest of individual trees to help determine what may cause the differences in yields. Though it was surprising that the vacuum tubing system produced the low- est quantities of sap, this was only a preliminary study without any repli- cated trials. Thus, future research should explore sap yields under vacuum at additional sites over the course of several years be- fore any conclusions can Figure 2. Average sap production from black walnut be made regarding the ef- trees at four locations during 2014 sugaring season. fect of artificial vacuum on walnut sap flow. that this report only covers the first year of what will ultimately be a long-term Another aspect of walnut syrup study. As with maple, the differences production that requires further at- in yields are likely to be significant tention is the large quantities of pec- between years based on local weather tin often found naturally occurring in conditions, so it would be premature the sap. Pectin can make filtering the to make assumptions based on one sap and syrup extremely difficult and year of data. The sample year, 2014, time consuming, clogging filters much was also very cold throughout March more rapidly than the sugar sand often and soils were deeply frozen due to found in maple syrup. There seems to a lack of snow cover, which could ex- be tremendous variation in the amount plain part of the low yields. Although Walnut: continued on page 37 this study suggests that it is unlikely that a walnut sugarbush will ever produce similar quantities of sap as a typi- cal maple sugarbush, there were a few trees on some sites that did produce large quantities of sweet sap in a similar manner as maples. It is possible that there are genetic differ- ences within black wal- nuts that allow some trees to produce large quantities of sap whereas others may produce very little. - ther research should ex- Figure 3. Avg. sap sugar concentration from black wal- plore the specific qualities nut trees at four locations during 2014 sugaring season

December 2014 35 Walnut: continued from page 35 Ewers, F., Ameglio, T., Cochard, H., of pectin produced between individ- Beaujard, F., Martignac, M., Van- ual trees and sites as well as the time dame, M., Bodet, C., and P. Cruiz- of the year that the sap was collected. iat. 2001. Seasonal variation in xy- We did some initial experimentation lem pressure of walnut trees: root with using pectinase, an enzyme that and stem pressures. Physiology. is designed to break down the pectin, 21:1123–1132. obtained from Carolina Biological. Our Farrell, M. 2013. The Sugarmaker’s Com- initial trials were not extensive enough panion: An integrated guide to produc- to come to any conclusions on the ef- ing syrup from maple, birch, and wal- ficacy of pectinase, but given the prob- nut trees. Chelsea Green Publishing, lems associated with filtering and the White River Junction, VT. 352 p. prevalence of pectinase in so many oth- er processing industries, this idea Naughton, G., Geyer, W., and E. Cham- deserves further attention. bers. 2006. Making syrup from black walnut sap. Transactions of the Kan- Finally, additional research is neces- sas Academy of Sciences. 109 (3/4): sary to explore the economics of pro- 214-220. ducing walnut syrup for existing sugar- makers. Although yields from walnuts are likely to be much less than from maples, it may still be a viable enterprise if the syrup 22427427 U USS R Routeoute 2 2 C Cabotabot | 8800-639-185400-639-1854 can sell at a high enough MModelodel 100E100E 800-639-1854800-639-1854 M2427odel2427 US100E US Route Route 2, 2Cabot, Cabot VT | • 800-639-1854 800-639-1854 price. 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