The recent warm spell had many maple producers fired up and ready to tap. If you frequent a maple chat forum such as Maple Trader you hear a lot of speculation on when, where, and how to tap. There appears to be as many theories on tapping as there are tap holes. Let’s look at the tapping process.
The first thing to remember about tapping trees, whether you tap early or late, is that you only have one chance to get it right. Making a mistake the first attempt can screw up the whole season. It is more important how you tap than when you tap. First, we need to take a look at the trees and determine which ones to tap. To do this, we follow a set of tapping guidelines that are published in the North American Maple Syrup Manual. Depending on whether you follow the traditional or the conservative guidelines you will be tapping a tree no smaller in diameter than 10 to 12 inches. This is where a recent study done by the University of VT Proctor Lab adds clarity to the ongoing debate. The research work was done by Dr. Abby van den Berg at Proctor at high yield sugar bushes throughout Vermont. High yield was operations with vacuum systems using 20 plus inches of vacuum to collect sap. What Dr. van den Berg found out was that the current conservative tapping guidelines of 12 inches in diameter minimum size was appropriate for tubing systems using modern high vacuum collection systems.
The study compared the percentage of functional and non-functional wood in the trees of different diameter and applications. Functional wood is new growth wood, the kind you can tap and get peak production. Non-functional is the dead wood that is left behind as a result of tapping. This wood is the stained non-productive wood that you see in cross sections of maples that have been tapped. At 12 inches diameter a healthy tree will regenerate enough new growth (90% or greater functional wood) to maintain tree growth and adequate sugar production to maintain tree health. Trees under 12 inches saw a steady decrease in the percentage functional wood at an earlier age. This is important because you want to consistently be tapping into new wood year after. If the percentage of functional wood is on the decline this makes it harder year after year to find new wood to tap. It could lead to a decline in overall tree health and productivity. A quick way to determine tree size is to use a rope 38 inches inches long. If you get to a tree and you can place the rope around the girth of the tree without the two ends of the rope touching then you have a tree at least 12 inches in diameter. There were other factors in the van der Berg study that could also influence the reduction of functional wood.
The standard drop line length recommended and used in the study is 30 inches. It was found that if the drop length was reduced, it in turn reduced the tapping zone of the tree. The result was a decline in the functional wood area at an earlier age. This is very important. As we work, innocently enough, our drop lines get shorter and shorter as repairs are made and old spouts are cut off and new spouts are replaced. Slowly but surely, this greatly reduces the tapping area on that tree. If you are following the new tap sanitation recommendation of replacing drop lines every other year you can overcome this problem of short drop lines by replacing them with new 30 inch drops. Also consider on trees with very large diameters that you may need an even longer drop line. Another factor is using the old style large spout. This will increase the size of the non-functional wood for each tap. It is always wise to use the new 5/16″ tap if you want to promote tree health.
The study at Proctor used a one and a half inch tapping depth with the 5/16″ spout throughout the study. One and a half inches is the correct tapping depth for today’s maple operations and maintaining that depth can be difficult. One way is to put a piece of tubing over the bit exposing 1 ½ inches of bit allowing you to reproduce that depth each time you drill. Also consider how you drill. Make sure you hold the drill straight drilling a round hole, angled slightly downward. If you wiggle the drill, you will have an oval shape hole that will leak sap and lose vacuum. Do this enough times and you will be losing vacuum all over the place. Use a sharp bit that cleans the shavings out of the hole. Shavings left in the hole will attract and promote bacterial growth. The spout must be seated properly but do not over drive the tap causing it to split on top and on the bottom. Use a light tapping hammer and leave the sledge hammer at home. Today most producers use cordless drills to tap. It is important to use a drill you are comfortable with – the new drills with Lithium batteries are light and are a good investment both in battery longevity and ease of handling.
Establish a tapping pattern that you use every year, such as 6 inches over and 6 inches up or moving to the opposite side of the tree. Do not try to tap a tree year after year on the south side because someone told you it would run early. With buckets expand your dumping zone to include high and low buckets. What is important is getting the job done right the first time. Remember there is no pride in bragging you tapped 1000 trees today if half of them are screwed up. Slow down and make your work count. Here is the website for the University of VT Fact Sheet on Tapping.