Tapping walnut trees for sap collection and syrup production provides a syrup producer the opportunity to tap into the new, growing, and potentially lucrative specialty tree syrup market. The bulk price for walnut syrup in West Virginia this past season ranged from $150-$250/gallon, with retail sale prices topping $500/gallon (Tonoloway Farm, 2020). To get there, potential walnut syrup producers need to know how and when to tap their trees to maximize sap production. During the 2020 sap flow season, Future Generations University, with a grant from the NE SARE program, conducted studies looking at the application of vacuum, spout design, tapping procedures, and the timing of sap flow in walnut trees. This paper presents part of the findings of that work.
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Details a study of 3/16″ tubing conducted in West Virginia.
Our objective in this 2020 study was to revisit walnut tree sap flow and to determine whether vacuum applied to sap collection lines would substantially increase the production of walnut sap. Along the way, we made some somewhat startling and troublesome observations and formulated a next generation of questions that need to be answered to allow a viable walnut syrup industry to develop.
During the 2019 sap season, Future Generations University, with funding from the West Virginia Department of Agriculture, began a series of tapping studies on tree species other than maple. We tapped and made syrup from black walnut trees. We had trouble developing the expected natural vacuum on the 3/16-inch lines, even though they had plenty of slope. We assumed that the problem was related to vacuum leaks associated with a poor seal in the soft wood with the minimally tapered spouts.
Accepted tapping practices for 7/16 inch spouts with no vacuum called for tap holes to be drilled 2-2.5 inches deep. Later practices for 5/16 inch spouts under vacuum, call for drilling the tree to a depth of 1.5 inches. The reason for the reduction in depth, was to reduce the occurrence of drilling into dead wood, especially on trees with a long history of tapping. This can lead to reduced sap yield. When the 2018 season left us with an unusually low sap yield, the question arose: does tap depth matter when the system is under vacuum?
This study showed that sycamore does produce a sweet sap flow that can be boiled down to roduce a syrup. That syrup had a nice taste, that some people say has a butterscotch like flavor. This is a new sap and syrup product, that will need more work to develop taping strategies that could lead to its commercial production. Likewise we need more information on the sap and syrup chemistry before we can provide guidance to potential syrup producers.
A 107 tap study area was established at John DalenÕs farm in Franklin WV. At this site we carried out a series of trials to learn about walnut sap flow, and to address sap and syrup production issues as they arose. We also collaborated with walnut sap producers in Palestine and Leon WV, and with Virginia TechÕs Catawba Sustainability Center in Blacksburg VA. The analysis section of this report is based on the work done at the Dalen farm study area.
When looking to expand the maple industry people often look at the large acreages of forested lands in the public domain. In West Virginia, 16.5 percent of the land is in public ownership, and in Virginia, 17.1 percent. Of that, the largest acreage is managed by the federal National Forest System (NFS). Sugarbush owners adjoining NFS lands might look across the line to tapable maple stands in the national forest. Private citizens or community groups could also look at public lands as a way to get in the business. In this study, we investigated an example of a community group, the Mt. Rogers Volunteer Fire Department and Rescue Squad, that is running a successful maple sugaring operation by tapping trees in the adjoining George Washington-Jefferson National Forest. We examined the sugaring operation and the impacts that the sugaring operation is having on the Whitetop community.
In a normal sap flow event, trees exude sap during the above freezing period and replenish that lost water by ÒsuckingÓ it up from the roots during the below freezing period. If on a tubing system, during this negative pressure period they tend to draw sap back into the tree from the dropline. Sap, once it enters the droplines, is quickly contaminated with microbes. When they are drawn back into the tree, tap hole closure is initiated. The problem is compounded in 3/16- inch tubing because, unlike 5/16-inch tubing, the smaller diameter collection tube remains full of sap. A Cornell study found that up to 12 feet of sap in a 3/16-inch tube can be drawn back into the tree during this recharge time. CV spouts are one proven method of limiting this drawback with 5/16 inch tubing. The question was: will they also be effective with 3/16-inch tubing that is full of sap?
Making maple syrup in the mild climate of southern Illinois is lesspredictable and more work. The sap seasons are longer, there is an almost certain need to freshen the tap holes, and the freeze-thaw cycles are less predictable.