Planning

The Ohio State Phenology Calendar: Understanding Nature’s Biological Clock (Part 1)

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A special thanks to Denise Ellsworth from OSU’s Department of Entomology for contributing her phenology expertise that makes this article possible!

Phenology, sometimes referred to as the world’s oldest science, is the study of recurring biological events and their relationship to weather and climate. Examples of phenological events include bird migration, flowering of plants, and the seasonal appearance of insects. Because the growth and development of plants depend on temperatures, phenological events of plants, such as bud swelling or flowering time, may be useful for monitoring short-term weather patterns. Likewise, scientists can detect long-term changes due to climate change by tracking the pattern of phenological events over many years.

Insects emerge earlier in warmer years than in cooler years, and plants bloom earlier too. The critical assumption in the use of plant phenology to predict other biological events is that the phenological sequence (the order in which events occur) remains constant from year to year even when weather patterns differ greatly. It is no mystery, even to a novice sugar maker, why plant phenology matters in maple. The quality of maple syrup is at stake! Once the phenological calendar for a sequence is established, the biological calendar is easily monitored to anticipate when maple syrup quality drops. If phenology can be grasped, this can greatly simplify the logistics of planning and scheduling monitoring programs, post-season clean-up and sanitization, and other critical activities. And using phenological sequence is valuable to a whole host of applications beyond just maple—beekeepers, naturalists, and gardeners also use the predictable patterns of nature to predict plant bloom and other biological activity.

On The Ohio State University Phenology Calendar website, degree-day data and related plant bloom and pest emergence sequences are accessible for any location in Ohio.  A degree-day is a measure of the amount of heat that accumulates above a specified base temperature during a 24-hour period. A degree-day is also referred to as a growing degree-day (GDD), heat unit, or thermal unit. One GDD accumulates for each degree the average temperature remains above a specified base-temperature over those 24 hours. Several degree-days can accumulate during a 24-hour period.  However, it is important to understand that degree-days have meaning only in relation to the base temperature that has been specified. The Ohio State Phenology Calendar uses 50 degrees F as the base temperature. To provide an example, if the average temperature over a 24-hour period is only 47 degrees F with a base temperature of 50 F, no GDDs would accumulate. However, if the 24-hour average temperature was 55 degrees F, 5 GDDs would be added to the phenology calendar (more on degree day calculation here).

To inform The Ohio State Phenology Calendar, daily temperature data from 12 OARDC Research Stations and three USDA-ARS weather stations located throughout Ohio are used to calculate cumulative GDD in real-time.  Calculations for locations between weather stations are extrapolated from climatic isotherms for Ohio.  Upon entering a date and any Ohio zip code, degree-day accumulation for that location is calculated, and the user is directed to the appropriate spot on the phenology calendar to determine what plants are blooming and what pests are active in their locale.  By scrolling through the full phenological calendar, it is possible to see what blooming and pest events have already occurred, as well as what has yet to occur.  And by clicking on the Summary tab, you can get a year-by-year breakdown of GDD count for the same date and zip code location across the past 6 years.

It is important to define a couple terms as we launch into species-specific phenology.  First bloom is defined as the first flower opening to expose sexual parts. Full bloom is when just one out of twenty buds is still closed while all others are open to expose sexual parts.

Of particular interest to maple producers, silver maple is listed first with 34 GDD at first bloom. A bit further down the sequence, silver maple reappears with full bloom at 42 GDD.  Red maple first bloom follows at 44 GDD just after silver maple full bloom. Red maple full bloom averages 75 GDD.  Sugar maple is not currently listed on the GDD calendar; however, it is believed that sugar maple tracks very closely with black maple – another of the “hard” maples.  While there is some uncertainty about the exact GDD timing for sugar maples, they are definitely “late bloomers” as compared to their “soft” maple counterparts.

The consistency in phenological sequence from year to year demonstrates that even one year of observation is useful to expand the phenological sequence to other plants or insects not included on the OSU calendar. This means that users can readily create, expand, and customize their own biological calendars by observing plants in first or full bloom and taking note of the GDD for that date on the OSU calendar. Many observers use a journal or excel file to track plant and insect activity from year to year, adding in new plants or insects of interest. These calculations can even be made by referring to photographs that show first bloom or full bloom; the photo’s date and location can be entered on the OSU calendar to determine the GDD for that event. Insect observations should be of developmental stages, such as egg hatch or adult emergence.

For the maple producer, understanding the predictability of nature’s patterns is crucial for better anticipating the end of each maple season. For years and years, sugar maple bud break was the traditional visual signal to take down buckets and end the sap season. Unfortunately, lots of poor-quality sap was made waiting for those first buds to break. Now we know that physiological changes occur within the tree prior to actual bud break that bring seasons to a close earlier. And sanitation issues that result in “sour” sap (due to bacterial build-up) halt most sap seasons before “buddy” sap is rampant. While we are excited to continue tracking sugar maple performance relative to GDDs, keeping an eye on the 100 GDDs mark is a rough indicator for when things are winding down. Some woods will shut down earlier and others will stretch a bit later, but when the Forsythia approaches full bloom in your yard – which occurs right around 100 GDDs depending on variety – you can be sure the end of your sugaring season is nigh.

New Article Series Launches Next Monday

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This short post will serve as a sort of guidepost, a table of contents or roadmap if you will, for the next month or so worth of content.  We are excited to bring you a 4-article series on maple phenology.  Phenology is a fancy word for describing nature’s calendar.  We’ll discuss one of the most practical and accessible tools for tracking phenology – the growing degree day, or GDD for short.  Second, we’ll seek to understand and document how GDD is related to species-specific patterns in maple bud and bloom timing and why that matters for maple producers.  Then over the course of two installations, Les Ober will break down why an improvement of one’s understanding of maple season timing is particularly important towards the season’s end and how you can minimize and prevent unwanted bouts with “sour” or “buddy” sap.  After all, our main goal is promoting sustainable production of high quality maple syrup!

What to Expect for the Rest of the 2021 Ohio Maple Season

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Just like snowflakes no two maple seasons are exactly alike.  No question about it, this season fooled me. After about 5 years of early tapping, along comes 2021.  During December and January, we experienced above normal temperatures leading to what many believed would be one more in a string of early tapping seasons.  Tapping in January has become almost routine across Ohio.  However, just like a deck of playing cards, every deck has 2 jokers.  This winter season we had two meteorological jokers.

The first was the presence of a strong La Nina with its trademark warmer and wetter weather conditions.  Hidden in the background far to the North was the second joker – the always volatile and never popular polar vortex.  A polar vortex is always a possibility during the winter months.  You never know when the jet streams will line up just right and push Artic air southward into our region.  This year we did not experience the full brunt of the vortex like we did in 2014.  The coldest air stayed well to the west of Ohio.  However, we did experience a cold spell that dominated 20+ days of February.

As result of the persistent polar vortex, the start of the 2021 maple season was pushed back until the last week of February and first couple days of March.  Even southern Ohio producers were forced to tap two to three weeks later than normal.  The first of March is not historically an abnormally late starting time for maple season in Ohio.  The one dominant factor that makes this season different is that our weather is still being somewhat controlled by a strong La Nina weather pattern.  The threat of an early warm-up and above normal temperatures are real.  And the first indication of that was the stretch of 60-70 degree temperatures experienced during the middle of the second week of March.  This was enough to trigger budding in red maples and silver maples of southern Ohio.

At the same time, many sugar camps in northeast Ohio set one day records for syrup production.  Sap flows were exceptional after the long cold spell of February.  As of March 12th, the same camps are reporting a half crop entering the third week of March.  The above normal temperatures experienced at the end of the second week, pushed the season close to the brink.  Conditions also caused a dramatic change in syrup grade, and Dark Robust and even Dark Strong profiles have mostly displaced the Golden grade of early season.

The next two weeks will determine the outcome of the maple season in Ohio.  OSU Climatologist Aaron Wilson is predicting a mixed bag of weather conditions for the rest of the month.  There will be some below freezing temperatures but nothing extreme.  For southern Ohio, the trend is for slightly above normal and for northern Ohio – normal temperatures.  Again, we may or may not see those colder low temperatures needed to reset the trees and delay budding.  What is also troubling is the lack of moisture.  2021’s recent precipitation trend is not typical for a La Nina year, and drier than normal conditions are slowly creeping into Ohio.  We need precipitation, snow preferred, to keep the sap flowing, but that key factor is largely missing in the forecast for northern Ohio.  At this stage, we need a hybrid of the two jokers to keep this season productive.

I will keep my prediction for the rest of March to myself, goodness knows the first two months of 2021 fooled me.  That said, I will be able to confidently predict the outcome the 2021 maple season in Ohio on the 15th of April.  What is it they say about hindsight?

 Les Ober, Geauga County OSU Extension

Upcoming Webinar (11/19): Climate Change Impacts and Risks to Southern Maple Production

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The maple syrup industry is impacted by both seasonal weather and long-term changes in climate. While the short-term conditions impact annual production cycles and quality, long-term changes in climate are having an impact as well. Temperatures across the maple syrup production areas of the US are warming, and climate change extends well beyond just temperature to include shifts in seasonal precipitation patterns and increasingly extreme events. Projections of future climate pose significant risks to the future of maple production across southern zones. Join the webinar (Register HERE) to explore the influence of weather and climate change on the maple industry and discuss the implications for the future.

Speaker: Aaron B. Wilson – Aaron is an Atmospheric Research Scientist at The Ohio State University, holding a joint appointment with the Byrd Polar & Climate Research Center and OSU Extension. He is also with the State Climate Office of Ohio.

The webinar is part of the Out of the Woods series hosted by Ohio State University, Future Generations University, and Penn State University.

 

 

CFAP Webinar for Maple Producers

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The news that maple is now included in the USDA’s list of crops eligible for Coronavirus Food Assistance Program relief is BIG!  For more details, you can click back to this recent post by Les Ober.

On September 1 at 7 PM, make plans to attend a webinar hosted by Ohio State University, Future Generations University (WV), and Penn State that breaks down CFAP for maple producers.  The webinar grows out of the region’s tri-state ACER collaborative.  Specific topics include how to determine your operation’s eligibility for CFAP, how to fill out the CFAP application, and other practical help to take advantage of the relief program.  Cindy Martel and Les Ober will be the speakers.

Register for the CFAP Maple webinar here.

Our team is proud that this hyper-relevant topic will open a brand new series of free webinars for maple producers.  The series will highlight diverse topics that enhance your maple business ranging from marketing and taxes to tree science and woodlot management.  The series is called Out of the Woods: Enriching Your Maple Business.

 

When to Tap?

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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

The Ohio Maple Syrup Season: Moving Forward?

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budded-red

Photo caption: Red Maple in Middlefield Township, Geauga County, Ohio, March 1, 2017

It is March 2nd, and we have just witnessed the warmest February on record in the Cleveland area. The 77 degree day that we experienced on Friday, February 24th, shattered every record for a high temperature in the month of February, and it was also the highest winter temperature in Cleveland for any winter month. The way the month of February ended cast a dark shadow on our ability to make maple syrup in Ohio. Now we are in March and the cold temperatures have come back but where does that leave us?

Many trees have already budded out. All of the silver maple and many red maples that are out in the open have full buds. The sugar maples though have not yet budded and this is one of the main reasons why we prize and select for this species of maple. Given the conditions we have had to date, one thing is for certain – if you have not tapped yet, the potential to make a significant amount of syrup is gone. The next warm spell will likely end the season for everyone.

Now let’s address the producers that have been making syrup and have the potential to make more syrup. If you have red maples, make sure you look at them very carefully or just pull the taps, especially trees in the open such as along a field edge or road side. Several producers with large populations of reds have called it quits altogether due to budding. For those with sugar maples, the potential is there to make more syrup, but you need to be careful not to spoil that sap by collecting sap from red maples too that have already budded.

At this point, a producer’s biggest enemy is bacteria. Everything needs to be cleaned out and drained. You could literally see high levels of bacteria building in the lines and tanks over the previous week of warm weather. Many producers just kept the vacuum pumps running during that period and hoped for the best. Many collected a fair amount of sap due to weather fronts that pushed through. I am certain it paid to operate the pumps keeping lines clear and tapholes as cool as possible. If you shut off the vacuum because the trees quit running, I hope you were using check valves because this would have given you some degree of bacterial protection at the taphole.

Now that the cold weather has returned, what kind of syrup will we make? The answer will come once your fire up the evaporator. If the sap is “buddy”, you will know it. And if it’s not, you’ll most likely be producing a darker grade of syrup. That is not necessarily bad because most producers made a good batch of Golden Delicate early on. If the producer chooses, the two could be blended but taste will determine that. You can blend for color but you cannot blend for taste. If your syrup has a slight off flavor from sour sap or budding, it will show up in the blended grade. There is virtually no way to mask a syrup’s off flavor once it is there, and there is no reason to ruin good syrup that you have already made. That is why some producers already chose to call it quits rather than risking a batch of off-flavored in the sugarhouse.

Producers that tapped in early January have had an average season. The biggest question is, after last year and this year, have we established a new normal for Ohio maple syrup production or maybe the two distinct zones of production in Ohio are just consolidating. I say this because if you produce syrup near the Ohio River, you would normally tap in January. If you live in NE Ohio you would normally tap in mid-February. Maybe we are now seeing a climate shift that will establish a universal tapping date for the entire state. After this year, producers must finally realize one can no longer tap solely by the calendar. If you produce maple syrup in Ohio, you must to be ready to go by New Year’s Day. If the season does not start until February, so be it – but at least you will be ready. Climate change is just that – change, and the only certainty in life is change. We change our systems, we change our tapping technology, we adapt.

Author: Les Ober, Geauga County OSU Extension

Should I Tap?

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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