Deciding Where to Tap
When trying to decide where to tap:
- Select an area on the trunk where no previous taps have been drilled
- Avoid drilling directly above or below tap holes from previous seasons
- Alternatively, locate an area where more than 2 inches of new sapwood has grown over previous tap holes and non-conductive wood
- This can be very difficult when you can’t see into the trunk, or where no systematic tapping pattern has been followed over the years
- Although southern exposures may thaw faster than shaded north facing sapwood, it is important to utilize the full circumference and height of the tapping zone when installing taps
Tapping below the lateral line
Recently, maple researchers have been testing the idea of installing tap holes below the lateral vacuum tubes on maple trees. Normally the tap hole is positioned above the lateral line with the intent of draining the spile and drop line between sap runs, to prevent sap from freezing and tubing connections from coming apart due to expanding sap ice.
The advantage of tapping below the lateral line will allow producers to tap lower on the trunk into areas that have not previously been tapped. A larger tapping zone on the trunk will significantly improve the availability of clear sapwood for tapping, and less need to drill more than one tap hole per spile, when fresh clear sapwood is scarce and hard to locate.
The downside is that bacteria are more likely to close up the taphole before the season is over. This can happen if the taphole is improperly drained. The tree sees bacteria as a threat, and will try to plug up its “wound” more quickly than if the taphole were kept clean.
Keep the following tips in mind if you try lateral tapping:
- use new spouts with periodically-replaced droplines
- Check-valves can be helpful, especially if you have a mechanical releaser
- make sure the tubing connection is facing downward
- if you still notice sap accumulation, it may help to turn the vacuum on periodically
- placing the spout and dropline below the lateral line may increase chance of animal damage
- sap tube collection systems that operate using high vacuum (25 to 28 inches of vacuum) may be able to keep sap tubing drained of sap between runs
Keep a close watch on spile connections at the tap hole and on tubing connections in the drop and lateral lines, as the industry gains confidence in this new tapping technique.
Preserving Sapwood: A Critical Consideration
Quickly growing new sapwood (annual growth rings) and preserving conductive sapwood is the objective of managing a healthy sugar bush. Every time a tap hole is drilled, a quantity of healthy sapwood around the hole will never flow sap again. This sapwood becomes darker and is called a stain column or non-conducting sapwood. The stain column remains permanently fixed inside the sapwood and enables the tree to maintain internal sap pressure during spring and summer to enable the canopy to form unhindered.
This happens because trees will react to tap holes as a wound near the end of the sap harvest season. Trees can stop leaking sap similar to our ability to stop the flow of blood from minor injuries. They will begin permanently plugging the hollow wood fibres inside the sapwood above and below the drilled holes.
Two models of stain columns to represent the approximate volume of good sapwood that is permanently removed from future sap flow.
Non-conducting wood accumulates inside the trunk with each passing year as trees are tapped. Therefore, minimizing the number of holes drilled into the tree will help preserve more sapwood for future tapping.
How to Preserve Sapwood
- Make sure your sugar bush is healthy
Healthy sugar bushes that are located on fertile soil and are managed using good forestry practices can generally sustain larger diameter tap holes, assuming that tapping guidelines are followed. Here, new sapwood will accumulate each summer to ensure there will always be an adequate tapping area on the trunk for maple syrup production. Click here for more on tree health.
2. Locate taps evenly around the tree
Concentrated tapping is not sustainable for the tree. Utilize the entire circumference of the tapping zone, not just the southern exposure since there are no differences in total sap yield.
This will ensure that all non-conductive wood is spread out adequately, to always have clear sapwood for future tapping.
3. Use smaller drill bits
Each tap hole generates approximately 20 to 30 cubic inches of non-conductive wood within the sapwood. Small drill bits (5\16th or 19/64th inch) will generate significantly less non-conductive wood than larger old-fashion tapping bits (7/16t h inch). Tapping crews must visualise under the bark where these stain columns are, to avoid drilling into stained wood that will not conduct sap.
4. Do not drill more than 2 inches
Non-conductive wood forms a little deeper than the depth of the drill bit. Limiting tap hole depth to no more than 2 inches helps reduce the stain column and less risk of drilling into an old deeper stain column having off-flavour sap.
The content in these pages was originally created by Todd Leuty (previous Agroforestry Specialist), and edited by Jenny Liu (Maple, Tree Nut, and Agroforestry Specialist).