Where to Tap

Table of Contents

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
A blue lateral tube coming out of a tree, attached to a blue mainline tube. An arrow indicates that the length of the lateral tube is 30 to 36 inches and that area is the tapping zone.
The tapping area on each maple tree should occupy approximately 30 to 36 inches (75 – 90 cm) of trunk above the lateral sap line for all tappable trees. This pictured tap with drop line is placed at the upper most location to show height, but could be placed anywhere in the tapping area, utilizing all sides of the tree. 

 

Two images side by side. The left photo shows two blue lateral tubes connected to a blue mainline tube. An arrow indicates the length from the taphole to the mainline is 30 to 40 inches. The right image shows much shorter lateral lines, with an arrow indicating that the tapping zone is only 10 to 15 inches.
A hand is holding a drill up to a maple tree. There is a red mark indicating where the previous year's taphole was located, and a shaded rectangle indicating the non-conductive sapwood resulting from that taphole. Two text boxes give directions on where to place the next year's hole. They say "10 to 12 inches up or down in pattern, but always above the lateral line", and "1 or 2 inches over".
  • 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.

Two images side by side. The left image has one maple tree in the foreground and one in the background. They are connected by a lateral line. There are two smaller tubes leading from the lateral line to tapholes located below it. The rightmost image shows a taphole with a dropline that is distorted from ice inside of it. The caption on the photo says "Kepping hte vacuum pump turned on may help prevent pooling of sap in the drop line to the spile between sap runs. During a hard freeze, researchers testing this concept have observed that spiles may push out of tap holes where sap has frozen and ice expanded int eh tubing and inside spiles at the tap hole. Producers who are testing "tapping below the lateral line" at their sugar bush can check spiles for a firm connection in the tree following a freeze.

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.

Someone holding up a vertical cross-section of a tree. There are tapholes scattered across the board, with dark brown streaks running vertically. The caption says "This board shows the distrubtion fo tap holes and resulting stain columns when the living tree was tapped for sap. Tap holes were spread fairly evenly around the trunk. A few tap holes encountered stained non-conducting wood from previous taps. Photo: Ken Elliott, MNRF."
Someone holding two vertical planks of wood up to a maple tree to demonstrate the approximate amount of non-conductive wood that results from one taphole.
Two models of stain columns to represent the approximate volume of good sapwood that is permanently removed from future sap flow. 

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.

Two images. Leftmost image shows a horizontal cross-section of a tree trunk with dark brown staining radiating outward, at points where the tree has been tapped. The rightmost image has a longitudinal section of a trunk, with long brown streaks running vertically where previous tapholes were located. The caption says "A cross-section and a longitudinal section of the trunk help us understand how healthy trees react to, and recover from tapping. This tree was tapped properly then thinned out as other nearby crop trees grew larger. Stained wood accumulates with each season as non-functioning sapwood. Stain columsn form in spring as internal plugs, to stop the flow of sap out of the tree. Small diameter spiles help minimize the volume of stain columns. With proper tapping, a healthy tree should grow new sapwood faster than stain column volume accumulates. Wood samples by Curle's Maple Products."

How to Preserve Sapwood

  1. 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.

A horizontal cross-section of a maple tree, with dark brown radiating from the centre. There is a thick layer of paler, untapped sapwood around the perimeter.
Stain columns become buried deeper into the trunk with annual growth.  The healthier the tree, the faster new sapwood will accumulate over top of old tap holes.
A vertical cross section of a tree trunk, with the dark brown tube of the taphole cross-section as well. An outer layer of unmarked sapwood overlays it. The caption says "About 20 years of annual growth since this taphole was drilled. The hole remains hollow, while the new annual rings of sapwood have healed it nicely."

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.

A horizontal cross-section of a tree, with many tapholes pockmarking one side and very few on the other. The caption on the pockmarked side says "No healthy sapwood = no sap (wood decay), South side tapping". The caption on the unmarked side says "Healthy sapwood = good sap (this tree died). North side."
An open tap hole and rectangular stain columns created by other tap holes demonstrate excessive tapping on one side of the trunk. Good clear sapwood on the other side of the trunk could have been utilized, spreading the non-conductive stain columns more evenly around the tapping zone.

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

A blue spile being held up to a plank of wood to demonstrate how deep the spile should go in the tree.

 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).