Sap Yields: Why CODIT and Non-Conductive Wood Matter

CODIT stands for Compartmentalization of Decay in Trees, and sugar maples are darn good at CODIT!  Mark Isselhardt, during the 2021 virtual Ohio Society of American Foresters spring meeting, gave an excellent microscopic and physiological explanation of how maple trees wall off and seal up old tapholes.

Why does understanding compartmentalization matter to a maple producer?  Compartmentalization creates the all-important non-conductive wood that sugarmakers try to avoid with each year’s new taphole.  And just in case you were wondering – how much does it matter?  Through work conducted at University of Vermont’s Proctor Maple Research Center, Mark Isselhardt document sap yield declines of 70-75% when a taphole intersects non-conductive wood.

When to Tap?

The last 10 days of January 2018 had some very good weather for sap flow. If you live in the southern states or even southern Ohio, the decision to tap was a good one because you are never guaranteed a season past mid March. However, the decision to tap early becomes a lot more uncertain for producers further north. I present three maps for your consideration. The top graph is the temperature forecast for NE Ohio from AccuWeather. In my experience, their 30 day forecasts have been reasonably reliable.  The solid orange line is the average historical high temperature for the given dates, and the solid blue line is the historical low average. The broken orange line is the daily high forecasted temperature and the broken blue is the forecasted daily low temps. Once we get past the 5th of February, it appears we are going to drop below normal and stay there through the end of the month. Again this is a 30 day outlook, but it does match up with what all of the local weather stations are predicting.

february Forecast

The next graph is NOAA’s Weather Forecast for February. This Graph is indicating we will have equal chances of being above normal, normal or below normal, at least for Ohio. Looks like the likelihood for above normal weather extends up through New England.

Februar Temp

The last graph is the AccuWeather Forecast for Underhill, Vermont, home of the UVM Proctor Maple Research Center. I picked this location because they do a marvelous job of tracking weather data. The temperature graph appears to be slightly milder than the Ohio graph, with a couple of above normal spikes.  The thing to notice is the sharp rise in daily low and high temperatures at the end of February.

Underhill

I hope this information will help to make your decision easier and that you will seek out these planning resources in future years. Keep in mind that these are long-range forecasts with considerable margin of error.

Author: Les Ober, Geauga County OSU Extension

Should I Tap?

I got up this morning (January 12, 2017) and it was 60 degrees! All I could think of was that a lot of my friends who make maple syrup saw the same thing I did and headed straight to the sugarhouse to find their drills. To say the least, 60 degrees in early January is unusually warm and the recent weather pattern has everyone scratching their heads.  The decision of when to tap is one of the most important decisions you will make in any given year – hear are my thoughts on the subject.

First a little science! To quote New York Maple Specialist Steve Childs, we need to know “how does sap happen.” Sap flow is the result of sap rising and falling through the tree’s vascular system known as sapwood. Sap flows to provide nutrients to all of the vegetative growth above ground. Sap flows from the roots to the very tips of branches nourishing the buds that will develop into leaves. This process is on a phenological clock that limits the amount of time that we have to intercept a very small portion of that sap to convert into maple syrup. Once the buds emerge or “break”, sap is no longer usable for syrup production. Sap rises because of fluctuation in spring temperatures that we call the freeze-thaw cycle. As a tree freezes, a suction draws nutrients and water from the ground and through the roots. Once the temperature rises above 32 degrees Fahrenheit, gases begin to form inside the tree which then pushes the sap through the sapwood all the way into the very tops of the branches. Considerable pressure is produced in the process. In fact, pressures have been measured at 40 psi (pounds per square inch). When you drill a hole in the tree sap leaks out into a bucket and continues until the tree quits pushing sap or it freezes again. We can increase that flow by applying vacuum to the tap with a vacuum pump and tubing. If temperatures stay warm, sap flow will gradually decline; however, sap may flow up to 72 hours without the repeat of the freeze-thaw cycle. Without freezing, the sap level in the tree drops below the taphole and flow stops. Once the temperatures drop below freezing, the whole cycle starts again. This is a very simple explanation of a very complex process.

What else may stop sap from flowing? Once a taphole is drilled into a tree, the maple season clock starts to run. Using buckets and open tapholes, that window of opportunity is around 4 weeks before the taphole starts to heal up and sap flow diminishes. This healing is the result of the taphole being exposed to air and from the growth of bacteria in and around the hole. Air dries out the taphole and supplies oxygen to bacteria that coat the hole with slime eventually sealing off the exposed sap wood – similar to what happens when you get a cut. Blood flows for a while but eventually it coagulates and the bleeding stops. A vacuum tubing system is different in that the taphole is not exposed directly to the outside air and sap is kept flowing under vacuum for a longer period of time. If operated correctly, the taphole will be kept free of bacteria for most of the season. This can be accomplished two ways. First, you can keep the vacuum running continuously whenever the air temperature is above freezing. This keeps the sap moving, keeps the lines clear, and keeps the taphole cool. Producers have found that they can gather enough sap during extended warm periods to make enough syrup to pay for the cost of running the pumps during that period of time. The other method is to us a vacuum system with check valves to prevent bacteria-laden sap from the lines being pulled back in the tree. A tree will draw sap from the lines just like a hose will siphon water from a tank when you turn the tap off. The sap, because it has been exposed to the tubing, has some amount of bacterial contamination – however slight – and will speed healing of the taphole if drawn back to the tree. Check valves close when vacuum is released, and these simple devices seal off the tapholes from sap backflow.

Now to answer the question – “Should I tap during an early warm spell?” My suggestion is first to obtain all the information from a variety of sources that you can about upcoming weather patterns. Next, consider your system. If you are a small producer or a backyard producer looking for the ideal 30 day window, January is most likely too early to tap. Your taps may dry out and you may miss some of the really good runs in late February and March. You could re-tap but that is hard on the tree and is never recommended. The best approach is to watch the weather and be ready to get those good runs in February and March. For those of us who have vacuum tubing. We can stretch the season with taphole sanitation techniques. Watch the weather and tap when the opportunity arises. You may get some very good early runs. If you are going to tap now make sure you change out last year’s spouts and/or use check valves. You have to create a closed system at the tree to prevent taphole healing. If you have enough taps, consider tapping the side of the woods that runs early now and then tapping the later running sections a bit later on the calendar, effectively spreading your season. The best you can realistically hope for is two months before your taps start to shut down. I have personally kept my system flowing from the 10th of February to the 10th of April with the use of check valves and continuous vacuum operation. No matter what you decide to do, it is a gamble. Here is hoping your decision pays off!

Author: Les Ober, Geauga County OSU Extension

How to Handle Extreme Cold Late Season Conditions in the Sugarbush

It is now the 20th of February and temperatures have dipped to 20 below zero. In Rome, Ohio, of central Ashtabula County the temps dipped to 39 below zero. Enough already! Last year at this time many of us in Northeast Ohio were already headed to the woods to tap. In 2014, we had extremely cold temperatures but they occurred in January. None of us will forget the “Polar Vortex”. This was a new weather term and it quickly became the definition of extraordinarily cold weather. This time around we have to go back 20 years to become reacquainted with a very old weather term “The Siberian Express.” This is cold air that is literally pushed across the North Pole and driven deep into the heart of the United States. The last time we had this kind of outbreak was in 1994. We set a cold record on January 21, 1994. However, that did not affect maple syrup production that year; in fact, Ohio had one of its better years producing 90,000 gallons of syrup in 1994. The only difference was that the cold weather came in January.  We also had a hard winter in 2008 and experienced a break out year with 150,000 gallon produced.

The secret to producing syrup in a cold year is to be ready to go when the weather breaks…and it will break. Another thing you may have to deal with is tapping into frozen wood. Trees are like glass, very fragile in cold weather. Drive a spout too hard and you run the risk of splitting the tree above and below the spout. This crack will leak not only sap but vacuum. On the other hand, if your spout is seated too loose, it will need to be reset once the tree has thawed out. Under these conditions it is always better to underdrive the spout than overdrive splitting the tree. In many cases, you will probably need to reset a large percentage of spouts installed under frozen conditions anyways. This is something that large producers deal with annually because they often start tapping early during very cold weather to minimize lost production.

Snow in the woods is another thing that you will have to deal with unless we get a big thaw. The snow can be your enemy and it can be your friend. Snow creates all kinds of problems. Mainlines and laterals can be pinned under the snow and gathering trails may be blocked. In this case, I would much rather have to deal with a few lines under snow than having to clear trails. The amount of snow at the base of your trees is your guide to what has to be done first. With mainlines you may have to do some shoveling in the areas where the lines are close to the ground or if they are pinned by a fallen branch. Be very careful digging out around saddles, you do not want to damage your saddle connections. If you damage a hole where a saddle is connected you will run the risk of creating a vacuum leak. In this case you may have to splice the mainline so that you do not run the risk of a vacuum leak. There is no real good way to seal a damaged mainline at the saddle connection, and these can turn into some of your worst leakage problems. With pinned laterals you simply cut the lines, pull them out from under the snow and reconnect. Try to do this at existing connection points to avoid adding more splices. In many cases the line is down because a limb has fallen on it. This means that all of the connecting points have been stressed resulting in possible vacuum leaks.

In most cases, a few warm days will melt the snow away from the lines. The big thing is to be tapped when this happens. Having a snow pack in the woods can be beneficial in that it will keep your woods cool and wet. A slow melt off of a snow bank will not only keep the woods cool during the day but will promote reflective cooling at night often resulting in below freezing temperatures. A good thing! The slow release of moisture from melting snow is additional moisture to be sucked up by the trees stimulating a good sap flow. Something that often occurs in cold weather is portions of a sugar bush exposed to long periods of sunlight (often southern exposures) will run first and areas that are more shaded like a northern slope will run last. Using the above facts as a guide, get your traditionally warmer areas tapped first and then concentrate on the colder portions. In cold years, the cool areas hold snow longer and tend to run very good towards the end of the season. This can be a real season stretcher. However, do not use this as an excuse to put all of your taps on the warm side of the tree. This is an old wives’ tale and a bad practice. It is always best to follow some form of systematic tapping.

A few closing thoughts on getting around in deep snow cover, aka, snowshoes. I have tried them with mixed feelings. This will be one of the best cardio workouts you will ever experience. Do not expect to go to the metro park, try them out, and then think snowshoeing your woods will be easy. Walking on a groomed trail is way different than walking in the sugarbush. The size of the shoe required is determined by weight. Use as small of a pair as you can in the woods to prevent getting snagged on brush. Yes they keep you on top of the snow but for me it was like trying to walk with a bushel basket on each foot. On our first adventure, my partner and I looked like Yogi Bear and Boo Boo going through the woods. And one of the first things I learned was that snowshoes can quickly turn into skis on a slope. You need to master the side step or risk a dangerous slide into a ravine. Been there done that, not fun! Yes, snowshoes get the job done and will get you across the snow; however, I will leave snowshoes to the thin athletic New Englanders and French Canadians who promote them.

Have a good start to the season and until then stay warm.

Author: Les Ober, Geauga County OSU Extension

When Will You Tap and Will the Trees be Frozen?

It looks like a cold one going into the first part of the 2014 maple season. I do not believe we will see many trees tapped during the month of January. That being said, there are always a few hardy souls in Southern Ohio that venture out into the cold, trying to tap before Mr. Groundhog leaves his burrow.

Looking at the 30-day forecast maps by NOAA Weather for the Ohio Valley and Great Lakes, the forecast is for more of the same. The weather pattern that has been bringing waves of cold air into the region all winter appears to be staying in place. We can expect very short warm ups between these low pressure systems. What has set this year apart from other similarly cold winters, is the extreme cold caused by the polar vortex drifting farther south than normal. Some agricultural forecasters are predicting this pattern of below normal temperatures and above normal precipitation to continue through mid-March, with the above normal precipitation continuing for an additional 60 to 90 days beyond that. The one thing to remember is that predicting weather more than 5 days in advance is an inexact science.

In a normal year, the low temperatures at the start of February would be in the twenties with highs reaching into the mid-forties. This sets up a well-defined freeze/thaw pattern. The freeze/thaw pattern does not begin in New England until early March. Their season typically runs through April, but Ohio is about a month earlier. If we continue with a prolonged period of cold weather running through most of February, this could have an impact on the season. And if the weather remained cold and then suddenly warmed up and stayed warm, we could be looking at a short maple season this year. One thing is for certain, no matter how hard you try, you cannot completely forecast a maple sugaring season so you should be ready to jump when conditions change for the better. Remember, the only weather that counts is the weather that occurs from the time you put the tap in the tree to the time you pull it out. All you can do is be ready and tap as soon as Mother Nature gives you the green light.

This year, early tappers will, most likely, will be tapping into frozen wood. This is very different than the last two seasons which were very mild, and producers tapped under unfrozen conditions statewide. Frozen wood presents a few problems. The first thing you need is a very sharp bit. There is more resistance in frozen conditions, and bits will become duller quicker. You should check your bits frequently and change them as needed. Today, many companies make bits that are designed to drill under frozen conditions and this is a very common practice in Canada – and as we all know, the Canadians drive the maple innovation market. Because tapping into frozen wood takes a little extra force, you need to take care and not drill an oblong hole. Producers also need to be very careful when setting the spout. It is very easy to split frozen wood and cause a leak at the top and bottom of the taphole. An oblong taphole or splitting can cause vacuum leaks, so steady your drill hand and go straight in allowing the drill to do the work. Then seat the spout very carefully with a proper tapping hammer. Once the woods thaw a bit, you will probably need to go back and check the taps resetting where needed. There is a little extra work required when tapping early but you know what they say about the early bird. In this case no worm, but a lot more sap.

Author: Les Ober, Geauga County OSU Extension

Tips on Using Vacuum and Maintaining Tap Hole Sanitation

Looks like Ohio Maple Producers may be headed into another sugaring season with unusual weather patterns. As of February 5th, 2013, there has already been a significant amount of new syrup made in NE Ohio. The real challenge is setting up your production system so that it can deal with the changes in the weather. You may say that there is nothing we can do about the weather; we have to accept what comes. That is right, however, you can change the way you produce syrup to take advantage of every opportunity that comes our way.  If you take a look at what happened in Ohio over the past several seasons you will notice some definite trends. Yield per tap dropped from .286 gallons of syrup per tap in 2008 to .169 in 2010. Last year, we once again lead the nation in Yield per tap (.244).  One of the main reasons for this was that favorable weather patterns enabled producers on vacuum tubing systems to collect a greater volume of sap on more days over the course of the entire season.  The end result was a huge average yield per tap. How you manage your system during the season is key.

Taphole sanitation has become the buzz word of the industry. Taphole sanitation is all about keeping your drop lines and spouts free of bacterial contamination. The piece of technological equipment that may have started it all is the Check Valve Adapter Spout. The warm weather in Ohio over the last several years has proven to be a good test for the new spout that is designed to prevent a back flow of bacterial-laden sap back into the tree. It works well in warmer climates like Ohio.

Solutions for taphole sanitation are based on research done at Proctor Lab in Vermont and the work done at Cornell University. What it comes down to is that you need to be replacing your spouts every year. Plain and simple. You should be replacing your drops every other year. And if you shut off your vacuum for extended periods of time during the season when it is not frozen, then you should consider using the Check Valve. The newest model goes directly on the line without the stubby adapter and looks very promising. If you run your vacuum continuously then one of the new polycarbonate spouts may be the answer. Check your drops frequently looking for bacterial buildup. Also this is a prime area where squirrel damage occurs so watch for leaks.  At the end of the season, make sure you get all of the sap out of the drops. The best way to do this is to clean under vacuum if you can. This removes the maximum amount of liquid out of the lines.

One question that comes up a lot is whether you should shut down your vacuum pump during extended periods of warm weather or let it run? Many producers are finding out that when you run the vacuum pump continuously, you will continue to collect sap even when the temperatures remain above freezing for several days. In most cases, the sap you collect will produce enough syrup to offset the cost of running the pump. In fact it is better to keep the pumps on and keep something moving through the lines. This cuts down on bacterial growth in the lines and the moving sap will keep the lines cooler. But it takes a good vacuum pump to run under warm conditions. The average vane pump (dairy pump) struggles in this environment. They are not designed to produce high vacuum over long periods of time. They are designed to work comfortably at 16 inches of vacuum. This is the vacuum that you use to milk cows. The best pump choice for extended high vacuum use is a liquid ring pump. They are cooled by water or oil and they hold up well under long periods of continuous use.

The last several years should have convinced everyone that tubing on vacuum pays. The Financial Analysis Guide released in Winter 2012 by The Ohio State University shows that the cost of production can be improved by installing and running a vacuum tubing system. It is clear that technology is and will continue to drive profitably and production in the maple industry regardless of what Mother Nature throws our way.

Author: Les Ober, Geauga County OSU Extension

Tapping Basics

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.

Author: Les Ober, Geauga County OSU Extension