Calculating the best tapping date

[DaveB]

With things being so wonky this year and being a scientist (meteorologist/IT guy by trade) I wanted to try and bring some "science" to the "art" of tapping and seeing if there is a formula for when to tap trees based on past data and current weather patterns. I've been at this for over 30 years and an old sugar maker that I learned most of what I know from told me when I was starting out to just tap around the same date each year and not pay too close attention to the weather forecast. I knew that I was mostly done by the end of March so I backed that up 6 weeks and have been tapping around 2/14 every year like clockwork.

This has mostly worked out but years like this I think I'm missing some early runs and since I know have access to vacuum systems, check valve spouts and long term forecasts that I never dreamed of 35 years ago I thought I should take advantage of that. I also have 40 years of weather records on my farm so I know what the weather has been like for the past 40 maple seasons and would like to see if there was a way to calculate when the best tapping date would have been based on the weather.

I did some searching and I saw one post about calculating degree days (http://mapletrader.com/community/showthread.php?37608-Degree-days-before-tapping%85.) to determine that but it doesn't look that that is a valid method. I also found an article by the good Dr Tim about using the average temperature in a long term forecast (https://mapleresearch.org/wp-content/uploads/mn1116weather.pdf) to determine the tapping date but no determination on what temperature is best.

I know there are other factors to tapping such as wind, rain/snow and barometric readings but in the end I think it comes down to when the trees start budding. That was clear to me this year and we had a prolonged period of extremely warm weather, including the warmest January I've ever had. We returned to "normal" winter weather and on days when the sap should have been flowing extremely well, I just wasn't seeing good flows. It almost seemed like the trees were thinking it was late March when it was still the end of February. Knowing that, is there a way to calculate how many degrees days it takes before the trees start responding like that? I'd like to look at past years and see if I could have spotted that.

[maple flats]

My method has mostly been to look at the 2 week forecast, and when that shows a few sap flow days I tap. I say mostly because about 8 yrs ago I had 3 college age workers as my only help, at that time I started fixing lines on Jan 2, and my goal was to be tapped by Jan 20-21, because my help had to be back at school then.
If you are on vacuum tubing it works fine being tapped ahead, if on buckets that won't work.

[littleTapper]

Well, this is my best year ever and I tapped on February 4th. So, that's clearly the best day to tap. Sample size of 1, all that's needed, right? Totally scientific!

:)

That out of the way, there may be ways to get predictions that are close, but jeez, things are so different year to year. I tend to look at long-range forecasts and then with how things have been going, gauge when to tap.

The data wrangler in me, since that's a part of my day job, would like to have free time to start crunching on some numbers. But, too busy making syrup!

[Sugar Bear]

With things being so wonky this year and being a scientist (meteorologist/IT guy by trade) I wanted to try and bring some "science" to the "art" of tapping and seeing if there is a formula for when to tap trees based on past data and current weather patterns. I've been at this for over 30 years and an old sugar maker that I learned most of what I know from told me when I was starting out to just tap around the same date each year and not pay too close attention to the weather forecast. I knew that I was mostly done by the end of March so I backed that up 6 weeks and have been tapping around 2/14 every year like clockwork.

This has mostly worked out but years like this I think I'm missing some early runs and since I know have access to vacuum systems, check valve spouts and long term forecasts that I never dreamed of 35 years ago I thought I should take advantage of that. I also have 40 years of weather records on my farm so I know what the weather has been like for the past 40 maple seasons and would like to see if there was a way to calculate when the best tapping date would have been based on the weather.

I did some searching and I saw one post about calculating degree days (http://mapletrader.com/community/showthread.php?37608-Degree-days-before-tapping%85.) to determine that but it doesn't look that that is a valid method. I also found an article by the good Dr Tim about using the average temperature in a long term forecast (https://mapleresearch.org/wp-content/uploads/mn1116weather.pdf) to determine the tapping date but no determination on what temperature is best.

I know there are other factors to tapping such as wind, rain/snow and barometric readings but in the end I think it comes down to when the trees start budding. That was clear to me this year and we had a prolonged period of extremely warm weather, including the warmest January I've ever had. We returned to "normal" winter weather and on days when the sap should have been flowing extremely well, I just wasn't seeing good flows. It almost seemed like the trees were thinking it was late March when it was still the end of February. Knowing that, is there a way to calculate how many degrees days it takes before the trees start responding like that? I'd like to look at past years and see if I could have spotted that.

I too pick 2/15 as my projected tap date. I pick this date because I don't want the first two weeks of March to pass me by without my taps being more than four weeks old. It is my belief that the first two weeks of March at my long lat produce the most sap and best syrup of any two weeks of the year. By Far. So I tap not to miss them with reasonably fresh taps.

This year I backed my start date up 9 days and taped on 2/6. The weather was just too darn CRAZY to wait to the 15th.

With that said, my best sap flow was in the second week of March this year where I was getting 16 inches of natural on 5/16th tubing and had back-to-back 100-gallon days of sap flow somewhere around the 8th and 9th of March. I set my record with at least 800 gallons of sap this year. I pulled my taps yesterday after a final small run of 40 gallons of sap. The season is over in these parts.

I am going to stick with my 2/15 start date and 3/1 through 3/14 "be ready" theory until the sun completely melts the polar caps.

And will accept the fact that I am not going to catch every run unless I have separate bushes to tap at different times of the year.

And will take note and file neatly into the back of my extremely forgetful brain, the fact that an extremely warm January is as much of a reason not to tap as it is to tap.

I do know of another sugar maker in CT who also happened to tap on Feb 6th and had his second-best season in his many years.

Giving in to January is kind of like giving up on March, and that is a mistake in sugaring across this belt of the range. That is well written in the evolutionary scripts of these trees.

That is of course my opinion and my conjecture and easily wrong in any one particular season but easily correct over time and multiple seasons.

[Swingpure]

I experimented with tapping at different times this Spring. In our area normal tapping time might be around mid March. Although I tapped some trees in December, I tapped more in mid February and the balance at the beginning of March. My February gamble may have paid off more if the polar vortex had not been disrupted.

That being said, the lesson I learned is that trees in February (for our area) do not flow the same as they would in late March or April. The hours of sunlight is much less and the duration of time that the temperature stays at a daily peak temperature is less. So in February the temperature might reach 41°/5° but only for a short while.

This might be the wrong term, but what I am referring to is the potential for a tree to flow. Given the same parameters of snow, etc, a tree tapped later in the tapping season has a greater potential for flow.

Of note, the trees I tapped on lines in December are still flowing, and just with the eye test looking at what is coming out of the lines in comparison to lines that were tapped later, they have at least equal flow.

Knowing what I know now, barring exceptionally warm Spring, I will wait for when the potential for flow is greater and I will wait until at least March 7 before I tap.

A caveat is that 2 hours south of us in Southern Ontario they had warmer temperatures and basically no snow and they tapped earlier than normal, with great results. The lack of snow was a factor in their early success, so there are many variables, which makes coming up with a calculation or formulae, to tell you when you should tap, very complex.

[DrTimPerkins]

There are a number of factors that influence when sap will flow. A degree-day calculator is probably not going to be enough to be terribly reliable unless you have a really good forecast of the upcoming weather from the selected tapping date to the projected flow date. Sap flow (especially early in the season) is not just dictated by temperature, but also by prior temperature (if it's been really cold it takes a while for the trees to thaw), sun (to help thaw), precipitation type and duration, wind, etc. Forecasts of temperature are reasonably good....but terrible for these other things.

The BEST time to tap for highest yield would be the day before it started to flow. However, given that it takes some time to get everything ready and tightened up (if on tubing), then people have to tap earlier. The amount of time varies depending upon how many people you have helping, how many trees, the terrain, the weather, and especially the depth of snow.

Any projection would rely tremendously on the forecast and/or would assume that the weather is going to remain on the same trend. I think we saw this year that it did in some areas, but definitely did NOT in others. Huge variation.

Producers also need to keep in mind their collection method (gravity or vacuum) and sanitation level to understand how long their tapholes will remain viable (and how well they will flow during that period).

Don't get me wrong...I like math...I like projections...I can clearly see where would be an interest in this. I just doubt it would be any more useful than choosing a date based upon historical averages and modifying slightly (ahead or back) based upon the conditions (snow, help, prevailing temps, etc.).

[DaveB]

I started going back through my weather & sugaring data and the best correlation I could find as a predictor of when the trees started slowing down their sap production was when the 15 day average temperature went above freezing. This year was tough because it never went below freezing in January but I've had other mild years like 2012 & 2002 where I was basically done by mid-March so tapping in January would have given me my optimum 8 week window.

Speaking of finding the optimum 8 week window, I've been going back through the data and finding the last date where the 15-day average temp was above freezing and going 6 weeks back from there. It looks like I have about two weeks after that date where the sap will run for a total of 8 weeks.

I've gone back so far to 2002 and the average date for when the trees started to slow down on sap production was mid-March. That correlates with being done at the end of March. I may move my tapping date up a week or two because I rarely collect sap in April and that would give me 8 weeks instead of the current 6 week window I'm giving myself.

For years like this year when the average temp is above freezing in January I may just have to tap in January but I need to look at the data better.

I'll share more data but wanted to share that observation from my data.

[DaveB]

There are a number of factors that influence when sap will flow. A degree-day calculator is probably not going to be enough to be terribly reliable unless you have a really good forecast of the upcoming weather from the selected tapping date to the projected flow date. Sap flow (especially early in the season) is not just dictated by temperature, but also by prior temperature (if it's been really cold it takes a while for the trees to thaw), sun (to help thaw), precipitation type and duration, wind, etc. Forecasts of temperature are reasonably good....but terrible for these other things.

The BEST time to tap for highest yield would be the day before it started to flow. However, given that it takes some time to get everything ready and tightened up (if on tubing), then people have to tap earlier. The amount of time varies depending upon how many people you have helping, how many trees, the terrain, the weather, and especially the depth of snow.

Any projection would rely tremendously on the forecast and/or would assume that the weather is going to remain on the same trend. I think we saw this year that it did in some areas, but definitely did NOT in others. Huge variation.

Producers also need to keep in mind their collection method (gravity or vacuum) and sanitation level to understand how long their tapholes will remain viable (and how well they will flow during that period).

Don't get me wrong...I like math...I like projections...I can clearly see where would be an interest in this. I just doubt it would be any more useful than choosing a date based upon historical averages and modifying slightly (ahead or back) based upon the conditions (snow, help, prevailing temps, etc.).

Appreciate the response Dr Tim. I know it's a nuanced process and that the best seasons (for me) follow what you've mentioned. What's interesting to me was looking at the drop-off of my collected sap was when my 15-day average temp went above freezing, at least for the past 20 years. On average that happens in mid-March for me and I'm usually done collecting by the end of March or two weeks after that date. In years where that date occurred earlier or not at all, I was usually done 2-3 weeks after that as well. Of course that just marks the end of the season and not when to tap but at least it gives me an average date and I can look at the extended weather forecast tools that are available and see if it makes sense to tap prior to that date or after.

Does Proctor make sap collection data available or at least dates of your last sap collected or boil? I see your weather data is available and I'd be curious if the same correlation I'm seeing works for your site as well.

[Sugar Bear]

I experimented with tapping at different times this Spring. In our area normal tapping time might be around mid March. Although I tapped some trees in December, I tapped more in mid February and the balance at the beginning of March. My February gamble may have paid off more if the polar vortex had not been disrupted.

That being said, the lesson I learned is that trees in February (for our area) do not flow the same as they would in late March or April. The hours of sunlight is much less and the duration of time that the temperature stays at a daily peak temperature is less. So in February the temperature might reach 41°/5° but only for a short while.

This might be the wrong term, but what I am referring to is the potential for a tree to flow. Given the same parameters of snow, etc, a tree tapped later in the tapping season has a greater potential for flow.

Of note, the trees I tapped on lines in December are still flowing, and just with the eye test looking at what is coming out of the lines in comparison to lines that were tapped later, they have at least equal flow.

Knowing what I know now, barring exceptionally warm Spring, I will wait for when the potential for flow is greater, and I will wait until at least March 7 before I tap.

A caveat is that 2 hours south of us in Southern Ontario they had warmer temperatures and basically no snow and they tapped earlier than normal, with great results. The lack of snow was a factor in their early success, so there are many variables, which makes coming up with a calculation or formulae, to tell you when you should tap, very complex.

Great commentary by all on this thread. With regards to the Rookie above, he already knows a lot more about this then I do and already makes a lot more syrup than I do. Must be the Canadian blood and the symbol on his national flag.

To bolster the Rookies point above, I will add that many years ago I read a cool article in the Wall Street Journal of all places ( a great newspaper at the time ) Not sure about today. The article was about what makes deer shed antlers. There was significant proof that deer shed antlers based on the amount of daylight hours in a day and that weather ( warm, cold, snowy, rainy) had little to do with it. The point of the article being that the angle of the sun at a given latitude was the most determining factor in when deer shed antlers, and by far.

Now I am not saying the same thing is true with Maple Trees.

But I believe it is a HUGE factor in when Maple Trees determine when their Triple Witching Hours of sap flow will be. The trees can react to a rising sun in the sky day to day VS a sinking sun in the sky day today. I.E. spring VS fall.

Late November and early December ALWAYS have great freeze thaw cycles, but we almost never consider tapping then. Even though some sap will flow then, we know better, and the trees know better too. But yes, they do flow sap when convenient opportunity arises.

But I try not to let that S me in, even in January regardless of the weather.

If the earth shifts on its axis to any measurable degree, I might change my plan accordingly. :o

[DrTimPerkins]

That being said, the lesson I learned is that trees in February (for our area) do not flow the same as they would in late March or April.

I think that lesson had been learned a long time ago by a great number of maple producers. As I recall, several folks here provided you with some advice on that subject several months ago.

It's difficult for producers sometimes to hold off when they get the itch that spring is coming and the weather seems good for a day or two. It typically takes more than that for good flows to happen. It is even more difficult when you hear about others out there tapping and even making syrup. Keep in mind that these early folks usually fall under a couple of different scenarios:
1. They only tap some of their trees early and tap the rest later.
2. They are in southerly locations and/or have normally warmer sugarbushes.
3. They are LARGE producers with tens of thousands of taps, so they have to start early to finish by the time the good sap flows start. They KNOW that some of their taps will be dry early, but a portion of them won't (given the difference in the time they were tapped). They also tend to be folks who have high vacuum and really good taphole/spout sanitation.


This might be the wrong term, but what I am referring to is the potential for a tree to flow. Given the same parameters of snow, etc, a tree tapped later in the tapping season has a greater potential for flow.

No, this is absolutely NOT correct. Sap will flow from trees whenever the conditions are correct. Sap flows will happen any time when there are freeze-thaw conditions. It is a nearly purely physical phenomenon. Said more precisely, if the conditions for sap flow are met, sap will flow irregardless of the time of year. In fact, we can place branches in the freezer any time of year and upon removing them, sap will exude from the ends. The trees don't have a calendar for when sap flows. They do however have a physiological time for various sap sugar content. This has only a marginal effect on sap flow.

That given, there is a much higher potential for the tree to thaw more quickly in March or April. That has nothing to do with the tree. It is due to solar influences (longer days, more sun) and the fact that the prevailing temperatures are such that the trees are closer to the freezing point and not deeply frozen (in which case they take a long time to thaw out). It has almost nothing to do with the "potential" for the sap to flow. The tree doesn't dictate the flow potential...the environmental conditions (mostly wood temperature...not air temperature) do.

The other influence regarding tapping time is taphole viability. This is related to sanitation and microbial growth in the taphole. Once drilled, the process of compartmentalization starts. We just don't see it because it happens inside the tree. Life functions happen (albeit slowly) even at really cold temperatures. Compartmentalization is slow when it is really cold, and picks up when it is warm (as does microbial growth in the taphole...the thing that elicits taphole compartmentalization and reduced sap flow rates). Tapholes that are open (on gravity) or tapholes where the equipment (spouts/droplines) are not well sanitized will "clog" faster than tapholes that are on vacuum (constantly pulling any sap AWAY from the taphole) and tapholes in which the equipment is new or well sanitized (or with CV spouts). This process happens fairly quickly for gravity collection....you can expect a taphole to remain viable AND produce well for only 4-8 wks (depending largely on wood temperature, with sap flow slowing down considerably near the end). On good, consistent vacuum with good sanitation, we can extend the taphole viability and high sap production rates up to 12+ weeks.

All of this is quite well understood. Not at all certain why we have to "learn" it again and again.

[DaveB]

That given, there is a much higher potential for the tree to thaw more quickly in March or April. That has nothing to do with the tree. It is due to solar influences (longer days, more sun) and the fact that the prevailing temperatures are such that the trees are closer to the freezing point and not deeply frozen (in which case they take a long time to thaw out). It has almost nothing to do with the "potential" for the sap to flow. The tree doesn't dictate the flow potential...the environmental conditions (mostly wood temperature...not air temperature) do.

The other influence regarding tapping time is taphole viability. This is related to sanitation and microbial growth in the taphole. Once drilled, the process of compartmentalization starts. We just don't see it because it happens inside the tree. Life functions happen (albeit slowly) even at really cold temperatures. Compartmentalization is slow when it is really cold, and picks up when it is warm (as does microbial growth in the taphole...the thing that elicits taphole compartmentalization and reduced sap flow rates). Tapholes that are open (on gravity) or tapholes where the equipment (spouts/droplines) are not well sanitized will "clog" faster than tapholes that are on vacuum (constantly pulling any sap AWAY from the taphole) and tapholes in which the equipment is new or well sanitized (or with CV spouts). This process happens fairly quickly for gravity collection....you can expect a taphole to remain viable AND produce well for only 4-8 wks (depending largely on wood temperature, with sap flow slowing down considerably near the end). On good, consistent vacuum with good sanitation, we can extend the taphole viability and high sap production rates up to 12+ weeks.

All of this is quite well understood. Not at all certain why we have to "learn" it again and again.

Isn't the same process with the tree going into dormancy in the fall also a measure of sunlight and temperatures? I've always understood that as a net sum gain for the tree. If the leaves can produce enough sugar for the tree to remain actively growing at a given temperature and the available light, they stay green. Once temperatures cool and the tree needs more sugar than the leaves can produce they start shutting down and enter dormancy. Isn't that the reason that the leaves start changing north to south? I would think the opposite is true in the spring where warming temperatures and more available light make it feasible for the leaves to do their thing.

I guess that's why I'm looking at the average two-week temperature. By 3/21 or thereabout daylight hours are equal across the maple producing realm and the season is wrapping up in the south when my average two-week temperature flips above freezing. In years where that happens earlier or later, I've been warping up earlier or later as well. I'm still looking at the data across a few places and it doesn't help with determining when to tap, but I do see the correlation.

[Swingpure]

I think that lesson had been learned a long time ago by a great number of maple producers. As I recall, several folks here provided you with some advice on that subject several months ago.

I do take advice given to me on this site seriously and have followed it many times. In this case I heard the advice, but much warmer than normal weather tempted me to experiment and if the polar vortex had not weakened, the decision may have turned out to be a smart one. As it is, i had fun experimenting and I have collected more sap and made more syrup than last year at this time. It also gave me the chance to use and learn the divided pan prior to the main start of the season. Having said that, next year I will wait.



That given, there is a much higher potential for the tree to thaw more quickly in March or April. That has nothing to do with the tree. It is due to solar influences (longer days, more sun) and the fact that the prevailing temperatures are such that the trees are closer to the freezing point and not deeply frozen (in which case they take a long time to thaw out). It has almost nothing to do with the "potential" for the sap to flow. The tree doesn't dictate the flow potential...the environmental conditions (mostly wood temperature...not air temperature) do.

I think I may have phrased it incorrectly and used the wrong term, but what I was trying to get across and what you explained better, is that flow potential is higher in March and April because of environmental conditions.


…. can expect a taphole to remain viable AND produce well for only 4-8 wks (depending largely on wood temperature, with sap flow slowing down considerably near the end). On good, consistent vacuum with good sanitation, we can extend the taphole viability and high sap production rates up to 12+ weeks..

It is a miracle the trees I tapped 87 days ago on December 27th are still flowing well. All of the freezing winter nights must not have counted in the 6/8 week countdown.

I do appreciate all of the advice given to me and in particular from an expert like yourself. All of the changes to my evaporator this year was from advice offered to me: base stack, 8” pipe, divided pan and float box.

[DrTimPerkins]

Isn't the same process with the tree going into dormancy in the fall also a measure of sunlight and temperatures? I've always understood that as a net sum gain for the tree. If the leaves can produce enough sugar for the tree to remain actively growing at a given temperature and the available light, they stay green. Once temperatures cool and the tree needs more sugar than the leaves can produce they start shutting down and enter dormancy. Isn't that the reason that the leaves start changing north to south? I would think the opposite is true in the spring where warming temperatures and more available light make it feasible for the leaves to do their thing.

No, your understanding of dormancy and the things that trigger it are wrong. Sap flow and dormancy are not related. Dormancy is triggered by both daylength and temperature, not by the amount of sugar the leaves are making or due to growth cessation. It is more of a physiological response to tree growth hormones. Most growth (root, basal, twig growth in most trees anyhow) is pretty much complete for the season well before leaf drop..by around mid-summer. After that trees (in northern climates) are putting carbs into storage. Leaves will continue with photosynthesis as long as it is possible. In fact, the light reactions continue irrespective of whether the dark reactions can occur, which cause issues with the physiology. The light reactions are like an engine that can't readily be shut down...so basically keeping your foot pressed down on the gas but with the car in park. Fall color formation (red) and breakdown of pigments involved in the light reactions helps to quell this problem. The leaves turn color and fall (it is believed) due to several factors, but carbs are shunted out of them before they drop. Maples do NOT need to undergo and then break dormancy for sap to flow. Sap will flow in maples whenever the physical conditions are correct, but in terms of maple sap collection, there is very often a large lag (due to thermal buffering since trees are big and dense), especially early in the season when nighttime temperatures are low and days are short, so warming is very transient.

[DrTimPerkins]

I do take advice given to me on this site seriously and have followed it many times. In this case I heard the advice, but much warmer than normal weather tempted me to experiment and if the polar vortex had not weakened, the decision may have turned out to be a smart one.

We almost always have some thaw periods each winter -- some winters more than others. Statistically, the chances of being correct in tapping at that time were really quite low. Your choice and your trees if you choose to do so, but it wasn't an experiment...we already know the answer to what happens most of the time if you tap really early with gravity methods.


It is a miracle the trees I tapped 87 days ago on December 27th are still flowing well. All of the freezing winter nights must not have counted in the 6/8 week countdown.

"Flowing well" in this case is qualitative. Most likely, even if they are flowing, the flow rates (and thus the amount you'd collect) will be far lower than if you'd tapped at a more typical time. Yes...you are correct that cold weather does slow/suspend the contamination/wound response in the taphole to some degree, but not entirely. Once a taphole is drilled, flow rates will decline over time and eventually stop. The rate at which flows diminish is related to several factors that are fairly well understood. Choosing a time to tap is important and encompasses several variables that all need to be considered to maximize the sap yield.

Sorry if any of this offends people, but I guess it is just annoying to me when people think they have a better handle on the subject than 200+ yrs of practice and dozens of research studies have shown us, and then seem surprised when it doesn't turn out the way they think.

[Sugar Bear]

No, your understanding of dormancy and the things that trigger it are wrong. Sap flow and dormancy are not related. Dormancy is triggered by both daylength and temperature, not by the amount of sugar the leaves are making or due to growth cessation. It is more of a physiological response to tree growth hormones. Most growth (root, basal, twig growth in most trees anyhow) is pretty much complete for the season well before leaf drop..by around mid-summer. After that trees (in northern climates) are putting carbs into storage. Leaves will continue with photosynthesis as long as it is possible. In fact, the light reactions continue irrespective of whether the dark reactions can occur, which cause issues with the physiology. The light reactions are like an engine that can't readily be shut down...so basically keeping your foot pressed down on the gas but with the car in park. Fall color formation (red) and breakdown of pigments involved in the light reactions helps to quell this problem. The leaves turn color and fall (it is believed) due to several factors, but carbs are shunted out of them before they drop. Maples do NOT need to undergo and then break dormancy for sap to flow. Sap will flow in maples whenever the physical conditions are correct, but in terms of maple sap collection, there is very often a large lag (due to thermal buffering since trees are big and dense), especially early in the season when nighttime temperatures are low and days are short, so warming is very transient.

I am wondering if sap flow within the maple tree and its range is more determined by daylight length ( regardless of temperatures which OBVIOUSLY have significant impact) then understood or recognized. Perhaps not just by the backyard sugars like me, but by those who study it day in, and day out and of course are a LOT smarter than I am on all fronts.

Perhaps this is why when a warm fall come's and we don't get a hard frost until early December the leaves still fall off the trees long before that first hard frost anyway.

The leaves never really shift their position on timing of their death(fall) and life(spring) much, regardless of temperature. Sap flow DOES but only a little more so.

And perhaps this is why in a year like this, when we have hardly a single iota of frost in the ground all year, and I tap on Feb 6th, I STILL got my best sap flow in the second week of March. Even though many very opportunistic sap flow days appeared in February, albeit there were some very warm shut down periods in February.

But yes, if I could afford/justify expensive pumps and 25 cents a kilowatt electric I would tap them all in December, keep it hermetically sealed with my intern crew, RO it in my $75,000 RO rig, line up the milk tankers, stow it away, boil it on day of choice and make sure I sucked every bit of sap out of every single tree all season long. And of course, these things will have a "steroidal" effect on nature. (I.E. turn a mediocre run in early February into a decent run)

But then there are guys like me and Swingpore trying to figure out how, why and when it makes sense to be practical with a bag of peanuts for maple sugaring equipment.

At least the bag of peanuts beats the equipment my brother and I used back in the early 1970's. That is for darn sure!

[Sugar Bear]

No, your understanding of dormancy and the things that trigger it are wrong. Sap flow and dormancy are not related. Dormancy is triggered by both daylength and temperature, not by the amount of sugar the leaves are making or due to growth cessation. It is more of a physiological response to tree growth hormones. Most growth (root, basal, twig growth in most trees anyhow) is pretty much complete for the season well before leaf drop..by around mid-summer. After that trees (in northern climates) are putting carbs into storage. Leaves will continue with photosynthesis as long as it is possible. In fact, the light reactions continue irrespective of whether the dark reactions can occur, which cause issues with the physiology. The light reactions are like an engine that can't readily be shut down...so basically keeping your foot pressed down on the gas but with the car in park. Fall color formation (red) and breakdown of pigments involved in the light reactions helps to quell this problem. The leaves turn color and fall (it is believed) due to several factors, but carbs are shunted out of them before they drop. Maples do NOT need to undergo and then break dormancy for sap to flow. Sap will flow in maples whenever the physical conditions are correct, but in terms of maple sap collection, there is very often a large lag (due to thermal buffering since trees are big and dense), especially early in the season when nighttime temperatures are low and days are short, so warming is very transient.

I am wondering if sap flow within the maple tree and its range is more determined by daylight length/daylight angle ( regardless of temperatures which OBVIOUSLY have significant impact) then understood or recognized. Perhaps not just by the backyard sugars like me, but by those who study it day in, and day out and of course are a LOT smarter than I am on all fronts.

Perhaps this is why when a warm fall come's and we don't get a hard frost until early December the leaves still fall off the trees long before that first hard frost anyway.

The leaves never really shift their position on timing of their death(fall) and life(spring) much, regardless of temperature. Sap flow DOES but only a little more so and can flow over a much wider span of time as compared to when leaves can fall and can start growing.

And perhaps this is why in a year like this, when we have hardly a single iota of frost in the ground all year, and I tap on Feb 6th, I STILL got my best sap flow in the second week of March. Even though many very opportunistic sap flow days appeared in February, albeit there were some very warm shut down periods in February.

But yes, if I could afford/justify expensive pumps and 25 cents a kilowatt electric I would tap them all in December, keep it hermetically sealed with my intern crew, RO it in my $75,000 RO rig, line up the milk tankers, stow it away, boil it on day of choice and make sure I sucked every bit of sap out of every single tree all season long. And of course, these things will have a "steroidal" effect on nature. (I.E. turn a mediocre run in early February into a decent run)

But then there are guys like me and Swingpore trying to figure out how, why and when it makes sense to be practical with a bag of peanuts for maple sugaring equipment.

At least the bag of peanuts beats the equipment my brother and I used back in the early 1970's. That is for darn sure!

[bigschuss]

I am wondering if sap flow within the maple tree and its range is more determined by daylight length ( regardless of temperatures which OBVIOUSLY have significant impact) then understood or recognized

Sorry if I'm being obtuse...you're suggesting sap flow is more determined by photoperiod REGARDLESS of temp...but then acknowledge that temp. obviously plays a significant role? It can't do both...play no role and play a significant role. Again, sorry if I am reading you wrong.



Perhaps this is why when a warm fall come's and we don't get a hard frost until early December the leaves still fall off the trees long before that first hard frost anyway.

The leaves never really shift their position on timing of their death(fall) and life(spring) much, regardless of temperature.


I live at the base of the highest mountain in Massachusetts. In the fall, the leaves begin changing 3 to 4 weeks on the summit of Mt. Greylock before they do in the valley. You can watch the changing colors descend down the mountain over the course of late Sept. to mid October. Yet the photoperiod for the summit of Mt. Greylock and the valley are the same. The opposite happens in the spring. Green-up occurs on the summit of Greylock a full month after it does in the valley...same exact photoperiod though.

So clearly these biological processes are not dependent on photoperiod alone. Indeed, temperature and local soil conditions would seem to be most significant contributors to leaf senescence in the fall.


But then there are guys like me and Swingpore trying to figure out how, why and when it makes sense to be practical with a bag of peanuts for maple sugaring equipment.


Use time tested standard practices and don't try to reinvent the wheel. This stuff isn't rocket science...we're boiling water. Commercial producers need to maximize their efforts and maximize their sap flow to maximize profits. I get that. But hobbyists like us? I try to maximize the fun and not get all wrapped up in the apps, and the data, and the stats, and polar vortex's, and GPM's, and that stuff.

[Sugar Bear]

Sorry if I'm being obtuse...you're suggesting sap flow is more determined by photoperiod REGARDLESS of temp...but then acknowledge that temp. obviously plays a significant role? It can't do both...play no role and play a significant role. Again, sorry if I am reading you wrong.


No that is not what I am trying to suggest. Poorly written on my part.

I am suggesting that sap flow or peak sap flow of the season is ALSO determined by daylight length and/or daylight angle in addition to ideal temperatures or specific weather, which of course, as we all know are required for profuse sap flow.

And perhaps the daylight length/daylight angle is more of a factor then we recognize, or it is believed to be.

Again ...

And perhaps this is why in a year like this, when we had hardly a single iota of frost in the ground all year, and I taped on Feb 6th, I still got my best sap flow, on these same taps, in the second week of March, even though many opportunistic sap flow days appeared in February. Albeit there were some very warm shut down periods in February, but those came after the opportunistic sap flow days in February.

Crazy warm winter we had but POOF ... like magic ... best sap flow in the first two weeks of March ... yet again. And yet on taps already 4 weeks old. And yet on taps that had ample opportunity to peak out in the second week of February just hours after they were tapped with no hard freeze up in the ground at that time.

So if that ( the above theory is true ) it makes all the more sense to find that ideal period (For my tapping range it seems to be March 1 through March 14) and tap no more than two or three weeks prior to that date period. And not drive oneself crazy year after year with when I should tap. This year I did three weeks prior instead of two weeks prior.

AND OF COURSE THIS ASSUMES YOU ARE SMALL GAME AND DONT HAVE TO START TAPPING IN AUGUST AND DON'T HAVE TO PAY A BUNCH OF SALARIES! Your own included.

[DaveB]

No, your understanding of dormancy and the things that trigger it are wrong. Sap flow and dormancy are not related. Dormancy is triggered by both daylength and temperature, not by the amount of sugar the leaves are making or due to growth cessation. It is more of a physiological response to tree growth hormones. Most growth (root, basal, twig growth in most trees anyhow) is pretty much complete for the season well before leaf drop..by around mid-summer. After that trees (in northern climates) are putting carbs into storage. Leaves will continue with photosynthesis as long as it is possible. In fact, the light reactions continue irrespective of whether the dark reactions can occur, which cause issues with the physiology. The light reactions are like an engine that can't readily be shut down...so basically keeping your foot pressed down on the gas but with the car in park. Fall color formation (red) and breakdown of pigments involved in the light reactions helps to quell this problem. The leaves turn color and fall (it is believed) due to several factors, but carbs are shunted out of them before they drop. Maples do NOT need to undergo and then break dormancy for sap to flow. Sap will flow in maples whenever the physical conditions are correct, but in terms of maple sap collection, there is very often a large lag (due to thermal buffering since trees are big and dense), especially early in the season when nighttime temperatures are low and days are short, so warming is very transient.

I'm sorry if I'm making it sound like I know better than 200+ years of other sugar makers. I always look to nature for my clues on when to tap even if I don't understand the full process of why. I'm also sorry if I implied that dormancy and were related. I wasn't.

What I was implying was that they both occur around the time when available sunlight and temperatures are either decreasing or increasing. In fact, on 9/21 and 3/21 everywhere will have an equal amount of sunlight available to them. However, on 9/21 some places will be at peak foliage and others will still have green foliage at the same time. The only difference between the two places is temperature for the most part. On 3/21 some places will be ending their maple season while other places (typically in the inverse of locations on 9/21) are just getting started. Again, the only difference is temperatures for the most part on those dates so sunlight isn't really a factor. It it is, please excuse me for not fully understanding the equinoxes.

Having said that, I anecdotally looked at my location and my sap flow as well as locations south of me and north of me and when they reported being done for the season. I then averaged the daily temperature at those locations for February, March and April. The date that those producers reported being done was very close to when the 15-day average went from below freezing to above freezing.

Again, I know temperature is not the only factor but from what I've seen that 15-day average going above freezing seems to correlate pretty well for when things wind down give or take a few days. Proctor has its own weather station I see online and you could do that yourself if you were interested. Look at the 15-day average and when your last good sap flows are. It seemed to be within two weeks of that date for the sites I looked at.

Like I said, I'm a meteorologist so I naturally am trying to apply some "science" to the art of sugar making. Being a maple researcher I think you do the same thing and I appreciate your insights!

[DrTimPerkins]

I am suggesting that sap flow or peak sap flow of the season is ALSO determined by daylight length and/or daylight angle in addition to ideal temperatures or specific weather, which of course, as we all know are required for profuse sap flow.

And perhaps the daylight length/daylight angle is more of a factor than we recognize, or it is believed to be.

There is ZERO evidence that day length/photoperiod/light angle have ANY effect on sap flow OTHER than how they affect tree temperature. Wood temperature is the dominant driving factor in sap flow.

Sap flow, growth, leaf drop and dormancy are all physiological functions that are well understood. The drivers and interrelationships are not terribly strong among this group. Sap will flow in wood vessels whenever driving forces are present. Those driving forces are dictated almost entirely by wood temperature.

[DrTimPerkins]

Like I said, I'm a meteorologist so I naturally am trying to apply some "science" to the art of sugar making. Being a maple researcher I think you do the same thing and I appreciate your insights!

No problem, but wood temperature (THE key factor) and air temperature are often quite different. Air temp is not the important factor.

Four things make this way more complicated than you assume:
1. Weather forecasts beyond about a week aren’t great, and even then tend to give a fairly broad range.
2. Wood temp forecasts don’t exist (and few places even measure this). In addition, trees are not isothermal - some parts of a tree might thaw while others can be simultaneously frozen.
3. The sap flow phenomenon relies upon a minuscule difference between freeze and thaw.
4. Microclimate in a forest is hugely variable, especially in terms of air temperature.

We understand the variables involved. We understand the processes involved. However wood temperature forecasting in a forest setting to predict a phenomenon that relies on a tiny difference in wood temperature is not yet feasible. Any forecast would be no better than looking to historical temperature averages and historical tapping dates. To aspire to that is great, but to think we are close to that point is not realistic.

Lastly, you assume we don’t have the data or haven’t made any attempts. You’d be wrong in both cases.

[DrTimPerkins]

In fact, on 9/21 and 3/21 everywhere will have an equal amount of sunlight available to them. However, on 9/21 some places will be at peak foliage and others will still have green foliage at the same time. The only difference between the two places is temperature for the most part. On 3/21 some places will be ending their maple season while other places (typically in the inverse of locations on 9/21) are just getting started. Again, the only difference is temperatures for the most part on those dates so sunlight isn't really a factor. It it is, please excuse me for not fully understanding the equinoxes.

This entire argument totally ignores or misunderstands the physiology of trees. In your example, why wouldn’t all the leaves on the same tree change color and then drop simultaneously ?

Sunlight/day length triggers some physiological processes along with temperature. In other cases (sap flow) day length has no effect (except as it affects wood temperature).

[Sugar Bear]

What I was implying was that they both occur around the time when available sunlight and temperatures are either decreasing or increasing. In fact, on 9/21 and 3/21 everywhere will have an equal amount of sunlight available to them. However, on 9/21 some places will be at peak foliage and others will still have green foliage at the same time. The only difference between the two places is temperature for the most part. On 3/21 some places will be ending their maple season while other places (typically in the inverse of locations on 9/21) are just getting started. Again, the only difference is temperatures for the most part on those dates so sunlight isn't really a factor. It it is, please excuse me for not fully understanding the equinoxes.


"Sunlight isn't really a factor", Unless of course sunlight just has to reach a certain level before stimulating the process of "peak" sap flow once proper warm temperatures and thawing have occurred. The season or peak season is farther out in the spring in the more boreal regions only because colder temperatures are not allowing it to come as early as the more southern regions.

My conjecture is, that the "TYPICAL POTENTIAL" for peak sap flow in any given coming season, will not come in say early or even mid-February in southwest CT or northeast VT for only one reason. The sun is too low in the sky at both latitudes at that time. The freeze thaw cycles in early February can dance like John Travolta and it will not change that. Yes, we can and do get runs at that time that make syrup and lots of it.

Otherwise, we would not hesitate to tap the great freeze thaw cycles of late November and much of December which frequently prevail across the greater Maple Range. And yes, for sure some sap flows then. But we know it's relatively weak so we don't tap them then even though temperature can be perfect. Sap flow is still not as strong even in January and into early February even when granted perfect thawing and perfect temperatures. That was clearly evident, on my taps, at my two locations, this season. And that has been evident in other seasons although not as clearly so because of colder conditions.

I am wondering. Does anybody know if sugar maples are cultivated on South America and how they do there if they do???

[Sugar Bear]

There is ZERO evidence that day length/photoperiod/light angle have ANY effect on sap flow OTHER than how they affect tree temperature. Wood temperature is the dominant driving factor in sap flow.

Sap flow, growth, leaf drop and dormancy are all physiological functions that are well understood. The drivers and interrelationships are not terribly strong among this group. Sap will flow in wood vessels whenever driving forces are present. Those driving forces are dictated almost entirely by wood temperature.

So are you saying there is no evidence that sunlight effects sap flow within the stem any other way then thermally over the course of a sap flow season. Correct?

[Swingpure]

So are you're saying there is no evidence that sunlight effects sap flow within the stem any other way then thermally over the course of a sap flow season. Correct?

Maybe another way of asking it, does sunlight affect wood temperature?

[DrTimPerkins]

So are you saying there is no evidence that sunlight effects sap flow within the stem any other way then thermally over the course of a sap flow season. Correct?

If we are talking solely about the physiology of SAP FLOW, then the vast majority of the influence is wood temperature. The vessel elements and fibers in the wood are DEAD while functional, so those other things have no way to influence SAP FLOW. Anything that affects wood temperature (sunlight, rain, snow, wind) is an indirect effect (they can influence wood temperature, which then influences sap flow). Sunlight, day length, etc. do not affect SAP FLOW except through their effects on wood temperature.

Going back more directly to the thread topic...air temperatures varies a little according to height, position, location, etc. Wood temperatures vary a great deal from one side of the tree to the other, from near the ground to the upper branches, and from a small portion of the woods to the next due to really minor changes in drainage, aspect, etc. Since the entire sap flow mechanism depends upon just the tiniest change from frozen to thawed, it is not realistic to try to predict when sap flow will occur with ANY degree of accuracy, especially from the early part of the season to the end. Weather predictions for air temperature beyond about a week aren't especially precise, and tend to revert to the mean temperatures based upon historical data. If that's the case, why not just use the same historical data to predict when tapping should start, and adjust a small and reasonable amount to account for the season.
Now if we start talking about stem sap sugar levels, dormancy, growth, fall foliage coloration, and leaf drop, then other things start to be involved as well.

[Brian]

Calculating the best tapping date

My Uncle Kenny always told me to take your average end date and back up 6 weeks and that is the date you should be all tapped in by. That has worked for me.

[Sugar Bear]

If we are talking solely about the physiology of SAP FLOW, then the vast majority of the influence is wood temperature. The vessel elements and fibers in the wood are DEAD while functional, so those other things have no way to influence SAP FLOW. Anything that affects wood temperature (sunlight, rain, snow, wind) is an indirect effect (they can influence wood temperature, which then influences sap flow). Sunlight, day length, etc. do not affect SAP FLOW except through their effects on wood temperature.

Going back more directly to the thread topic...air temperatures varies a little according to height, position, location, etc. Wood temperatures vary a great deal from one side of the tree to the other, from near the ground to the upper branches, and from a small portion of the woods to the next due to really minor changes in drainage, aspect, etc. Since the entire sap flow mechanism depends upon just the tiniest change from frozen to thawed, it is not realistic to try to predict when sap flow will occur with ANY degree of accuracy, especially from the early part of the season to the end. Weather predictions for air temperature beyond about a week aren't especially precise, and tend to revert to the mean temperatures based upon historical data. If that's the case, why not just use the same historical data to predict when tapping should start, and adjust a small and reasonable amount to account for the season.
Now if we start talking about stem sap sugar levels, dormancy, growth, fall foliage coloration, and leaf drop, then other things start to be involved as well.

I understand and it makes sense, and it parallels my experience with my trees.

Perhaps it's that in the first two weeks of March the rays of the sun are just producing enough thermal benefit to the wood such that it always causes me to get to peak flow in that time frame.

Do you think a Red Maple might flow earlier then a Sugar Maple in the exact same aspect ( just a few feet away ) because the wood is softer and might warm up faster? I would imagine the ideal wood flow temperature is the same in both trees.

[Sugar Bear]

Calculating the best tapping date

My Uncle Kenny always told me to take your average end date and back up 6 weeks and that is the date you should be all tapped in by. That has worked for me.

That is similar to my concept, but mine is take your average peak flow date and tap three weeks prior to that. Give or take up to a week based on unseasonably cold or warm weather.

It would be cool if all Maple Traders were to disclose their peak flow rate date and location each year. For me it is clearly evident each year and would imagine it is for most producers.

[maple marc]

Given the uncertainly of weather, does it make any sense to stagger your tapping, especially for producers on gravity/buckets? Dr. Tim, you hinted at this. You might call this a probabilistic approach--hedging your bets so to speak. Pick a day when that first run looks imminent and place maybe 60 to 70% of your taps? Pick a number. Then 2 weeks later place the balance.

[DrTimPerkins]

That is similar to my concept, but mine is take your average peak flow date and tap three weeks prior to that. Give or take up to a week based on unseasonably cold or warm weather.

Whatever works for you is the way to go. The length of time to tap prior to good flows depends largely on the technology you're using (gravity vs vacuum), how many taps you have, how much labor you have, and how deep the snow is.

[DrTimPerkins]

Given the uncertainly of weather, does it make any sense to stagger your tapping, especially for producers on gravity/buckets? Dr. Tim, you hinted at this. You might call this a probabilistic approach--hedging your bets so to speak. Pick a day when that first run looks imminent and place maybe 60 to 70% of your taps? Pick a number. Then 2 weeks later place the balance.

That strategy can work well if the time between tapping and good flows is long and if you have a sufficient number of taps. Those with a huge number of taps do that as a consequence of their size. They may start tapping around the holidays, and finish just a short time before good flows are normally expected in their area. Of course, the early taps may not be as productive (they have lower sap flow rates) towards the end of the season than the trees tapped later, but that is an acceptable tradeoff given the circumstances.

[DaveB]

This entire argument totally ignores or misunderstands the physiology of trees. In your example, why wouldn’t all the leaves on the same tree change color and then drop simultaneously ?

I wouldn't expect every leaf on a tree or area to change simultaneously due to the fact that not every leaf or tree is going to be subject to the same amount of daylight and temperatures. There are microclimates that make a place warmer or cooler for a number of factors and even though the number of available daylight hours is the same, not every leaf is going to receive the same number of hours of sunlight due to shading and the movement of the sun.


Going back more directly to the thread topic...air temperatures varies a little according to height, position, location, etc. Wood temperatures vary a great deal from one side of the tree to the other, from near the ground to the upper branches, and from a small portion of the woods to the next due to really minor changes in drainage, aspect, etc. Since the entire sap flow mechanism depends upon just the tiniest change from frozen to thawed, it is not realistic to try to predict when sap flow will occur with ANY degree of accuracy, especially from the early part of the season to the end. Weather predictions for air temperature beyond about a week aren't especially precise, and tend to revert to the mean temperatures based upon historical data. If that's the case, why not just use the same historical data to predict when tapping should start, and adjust a small and reasonable amount to account for the season.
Now if we start talking about stem sap sugar levels, dormancy, growth, fall foliage coloration, and leaf drop, then other things start to be involved as well.

To be clear, that was the original intent of the thread - to look at historical data as a guide for the current season. I really wasn't trying to come up with some numerical sap flow model like we have numerical weather prediction models. My observation about the 15-day temperature average is purely anecdotal but matches up well with my sap collection record. That gives me a good average date for when the season ends and I can start looking at weather models about 8 weeks prior to that to see if it will be warm or cold going forward and decide if I should start putting the taps in or not.

I know we don't have precise air temperature prediction beyond 5-7 days, but there are tools that allow a forecaster to blend different models to at least get an understanding of where temperatures are going relative to "normal". One I use is an ensemble based model and I can see up to 16 days out. This is one of the reasons I waited on tapping in January despite the mild weather that we had. The models were consistent that the pattern was going to flip (and it did) and we had more seasonable weather. The problem was that because we missed long prolonged cold air masses, my trees were acting like it was late March and not producing as much sap as they usually do.

Here's a site that I use that shows the ensemble models along with an mean and you can see the trend relative to the historic average. You can adjust the location by clicking on the map.

https://www.wxcharts.com/?panel=default&model=ecmwf,ecmwf,ecmwf,ecmwf&region=eusa&chart=overview,850temp,accprecip,2mtemp&run=12&step=003&plottype=ens&lat=42.048&lon=-72.418&skewtstep=0

[DaveB]

My Uncle Kenny always told me to take your average end date and back up 6 weeks and that is the date you should be all tapped in by. That has worked for me.

That's pretty much what I do. In my case I've always looked at the end of March as the end of my season and backed things up 6 weeks to the middle of February and tapped then. I started averaging the dates for when my season starting winding down and going back 42 days (6 weeks) to figure out and average date of when I should be tapping. I figure that will give me an 8 week window of time since my taps are on vacuum.

The problem for me comes when we have a year like this when its so mild. Technically I could have tapped a month early but I still waited for February because I knew more seasonable weather was coming.

I think for most years making a decision +/- 2 weeks from the average tap date is fine. For mild years I would now do the tapping as soon as temperatures will following a freeze/thaw cycle. For me that would have been January.