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  • Does high heat matter for fig development and ripening?

    https://www.ourfigs.com/forum/figs-h...-olympian-woes

    In the above recent thread (see Post #8, Comment 11), I raised an issue that I'd like to highlight here. How does heat affect fig development and ripening?

    In the comment, I make the point that << The average high temperatures in the Azores in July and August are 77 and 75, respectively. In Zadar, it's 83 and 83. In Ischia, it's 87 and 87. >>. For comparison, Philly's average high temps are 89 and 87. Providence RI's are 83 and 81. My inference is that the northern U.S. is perfectly suitable for figs. Northern locations seem warm enough.

    In the comment, I also make the point that fruit set seems to require ~30 days at warm enough temperatures, where 75 F definitely appears warm enough. As I posted a few months ago, 6 trees of 5 varieties growing under LEDs in my 75 F basement all set fruit in ~30 days. Florea and BMkk performed the same. This leads me to believe that 75 F is above the temperature threshold for fig fruit set. If that's right, temperatures over 75 F don't matter. I challenged growers to show me examples of faster fruit set. Nobody did. My tentative conclusion is that heat over 75 F is superfluous for fruit set.

    Here I'm moving on to ripening, specifically the time between fruit set and ripening. It appears to me that the earliest varieties, such as Florea and Ronde de Bordeaux, require ~60 days at temperatures above 60-65 F. But maybe higher heat matters. So I'm asking here:

    1. Does anybody ripen RdB or Florea in <60 days?
    2. Does anybody ripen Mt Etna is <72 days?

    In both cases, I'm counting days between (a) observable bb-sized figlets and (b) full ripe fruit. If higher heat matters, show me.
    Last edited by jrdewhirst; 07-15-2021, 08:30 PM.
    Joe, Z6B, RI.

  • #2
    I will add my ripening times from fruit set to ripe later this season. I have documented a couple hundred varieties first fig set. Heat definitely helps with ripening times as many of you start to ripen some varieties before me, despite my season starting a couple months earlier. I’m always amazed when I start seeing you all post ripe fig pics of varieties that, sometimes, are not even close for me.

    I follow your posts religiously and hope to learn from them.
    Eric - Santa Barbara, CA Zone 10a

    Comment


    • jrdewhirst
      jrdewhirst commented
      Editing a comment
      Thanks, Eric. FWIW, my question is not whether warmth matters -- there's no debate about that. It's whether high heat matters.

      Expressing this more precisely, the question is what the shape of the curve is relating (a) warmth to (b) growth and ripening. People probably agree that fig trees make no material progress at temperatures <50 F and minimal progress at 50-60 F. It seems, however, that figs can grow and fruit at >60 F and definitely at 65-70 F. In past research using ripening data from forum members, I couldn't find any evidence that ripening time (start of season to picking) was accelerated by temperatures above roughly 75 F. [But admittedly, there was limited data. More observations from growers in warm zones would be very helpful.]

      Continuing, we can imagine the curve as a sloped line connecting two asymptotes. Below X degrees F, no growth occurs; above Y degrees F, no growth occurs; between X and Y degrees, growth increases with temperature. But how fast?

      I'll toss out s straw man for discussion: For figs, X is ~50 F, Y is ~100 F. And the slope rises very sharply between 60 F and 80 F, but the incremental benefit above 80 F is minimal.

  • #3
    @TheMillenialGardener --

    << I've been picking RdB for a week. We were still getting hard freezes on April 3, here, so my tree had next to no activity on it. I went from the first buds to picking ripe fruit in 99 days. If you go to this video right here and skip to 14:37, you can see my RdB on May 8 >>

    I'm confused. You show potted Pastiliere and Black Madeira with lots of growth and fruit. But I didn't hear you mention Ronde de Bordeaux. You then show in-ground trees that are much further behind. Is RdB one of those?

    << I went from the first buds to picking ripe fruit in 99 days. >>

    This is perfectly consistent with what I've experienced here, especially since many of your April days were cool. For RdB, it's basically ~30 warmish days for fruit, then ~60 warmish days to ripen. Last year a nearby friend picked after 57 days.

    I'll assume that the producing RdB is one of your in-ground trees.

    << That would mean I was harvesting ripe RdB's 64 days after that tree was filmed, which had hardly any growth on it, and I don't think any figlets at that stage. Given how little growth was on that tree, I would estimate my RdB's probably ripening in the 50-something day period, but it's just a guess based on that video. >>

    Agreed. If the tree fruited 7-10 days later, which seems plausible, you'd have ripened those fruits in 54-57 days. That's at the fast end of the data I've seen, but not grossly out of line. And possibly it suggests that more or less heat can slide ripening from 55 to 65 days for RdB.
    Last edited by jrdewhirst; 07-16-2021, 08:56 AM.
    Joe, Z6B, RI.

    Comment


    • #4
      Originally posted by Evdurtschi View Post
      I have documented a couple hundred varieties first fig set.
      Evdurtschi Is your document public by any chance? Would love to see that list for my own reference.
      East Coast, Zone 7a
      WL: Panache, Boysenberry Blush, CdDB

      Comment


      • Evdurtschi
        Evdurtschi commented
        Editing a comment
        Not yet. It is still a work in progress. I will make it available at the end of the season

    • #5
      For grins and giggles I threw a couple non-producing trees in my shaded greenhouse to see if the Heat alone can get their juices flowing. So far so good.

      theyre not RdB or Florea but will be interesting to see if heat alone (with minimal sunlight & zero direct sun) will make it fruit
      wnc Z7a Hominy Valley
      wish list: a world without Invasive Pests

      Comment


      • #6
        My average temps in July and August are both 81. The problem here is the overnight low temps averaging 53 and 52 respectively. Daytime heat isn’t the problem. We have 5-6 months of 65*+ days from May to October. The overnight lows and the temperature swing I think is what slow us down so much.
        Oregon, Z 8b. No YouTube channel.
        No spin, no hype. Just enjoying the hobby and always learning.
        WL: paillettes à licorne, Lloral, cucurella, Blava flor, curio de bou, santmartina.

        Comment


        • #7
          jrdewhirst,

          I agree with Sod, the issue isn't about the average "High" Temperature, its the average Daily Temperature taking into account night time Low Temps. I'm in a similar situation in zone 5B with night time temperatures usually in the 40's and 50's well into July and also in September at the end of my growing season when figs are ripening.

          As you know, I'm an advocate of using the GDD base 50 for fig ripening and planning, it easily translates to temperature and time.

          For example;
          jrdewhirst = [ 75 + 75 / 2 - 50 = ] 25°
          Sod ......... = [ 81 + 53 / 2 - 50 = ] 17°

          Anyone could calculate the exact amount of heat / time and its effect on development and ripening, but I just use it as a general reference.

          BTW, You can use a simple Digital Lux Meter to calculate the actual amount of Light that the fig trees are getting, their DLI (Daily Light Integral)

          Edit;
          Joe 30 days; 30 * 25° (day) = 750° days
          Sod 30 days; 30 * 17° (day) = 510° days [ 750 / 17° = 44 days ]

          Joe 60 days; 60 * 25° (day) = 1500° days
          Sod 60 days; 60 * 17° (day) = 1020° days [ 1500 / 17° = 88 days ]

          Another example comparing "Locations" and how their temperatures can affect the days / time to ripen, elapsed time using GDD (Growing Degree Days);
          Joe Breba; 1500° / 25° (day) = 60 days
          Sod Breba; 1500° / 17° (day) = 88 days

          Joe MainCrop; 2500° / 25° (day) = 100 days
          Sod MainCrop; 2500° / 17° (day) = 147 days

          Last edited by AscPete; 07-16-2021, 11:25 AM. Reason: added Edit, Basic examples of using GDD for "ripening time" comparisons...
          Pete R - Hudson Valley, NY - zone 5b

          Comment


          • #8
            For what it’s worth, our average lows only appear to be a couple degrees off. Highs maybe 7-8 degrees. I believe you’ve estimated that mine start ripening about 2-3 weeks ahead of yours. Note that mine do generally start to wake up early/mid April when I’ll keep the garage door open or bring them outside if the two week forecast doesn’t predict frost. I believe you don’t generally bring yours out until mid May?
            You may only view thumbnails in this gallery. This gallery has 1 photos.
            Don - OH Zone 6a Wish list: Zaffiro, Moro de Caneva, Nerucciolo d'Elba, Bordissot Blanca Negra, Rubado

            Comment


            • jrdewhirst
              jrdewhirst commented
              Editing a comment
              Thanks, Don.

              I keep my San Pedros under cover until mid-May or at least until the forecast says that nighttime temperatures won't drop below 50 F. You can see from the graph that my average low hits 50 F roughly mid-May.

              I generally take my Common figs out when I think / hope that the low temperature won't drop below 40 F. The average low hits 40 F in early-mid April but to be safe I usually end up waiting until the 3rd-4th week, depending on the forecast.

              Meanwhile, I think the graph illustrates well how your weather warms up earlier than mine. Just as an example, the average high temperature seems to hit 65 F roughly 3 weeks earlier there.

          • #9
            I know cool temperate will increase the days for ripening time. My M10(Florea) tooks 78 days(pea size at June 18th and in the mouse Sept 6th) to ripe last year. I am sure the heat will reduce the days, but probably 60 day is the limit?
            Richmond, BC, Canada Zone 8A
            WL: Fioronne Oro

            Comment


            • jrdewhirst
              jrdewhirst commented
              Editing a comment
              standalonus -- This is good data for the impact of cold. My Florea sets fruit roughly the same time as yours but ripens roughly August 15. So it seems that cold (or something!) had a material impact.

              I'd like to check your daily weather data for last season. Can you suggest a source? Thx.

          • #10
            AscPete Sod --

            Yes, I agree that cold nighttime temperatures can be a drag. But I'm guessing that the questions of (1) heat requirement, and (2) cold impact are separable.

            Returning to the focus question re heat per se, I'll go back to the data from the Azores. As noted, the average high temperatures for July and August are 75 and 77 F, while the average low temperatures are 64 and 66 F. So the amplitude of the daily cycle is quite modest. As a result, there's no adverse impact of any more severe cold, so we can assess the requirement for heat without that noise. And figs seem to grow and ripen fruit quite fine there without more severe heat.

            Average lows here in Providence are similar -- 64 and 63 F. Philly is 72 and 70 F. Raleigh is 70 and 69 F. All fine.

            But Portland is different. The average highs are 80 and 80, the average lows are 57 and 58 F. So I can see that cool nighttime temperatures could be a problem.
            Joe, Z6B, RI.

            Comment


            • AscPete
              AscPete commented
              Editing a comment
              jrdewhirst ,
              I understand that you're looking to formulate an exact relationship between heat and ripening, but most fig trees are growing in ambient environments with varying temperatures with an adequate "range" of good growing temperatures . A researcher would need to create a 24 hr temperature controlled environment, but its probably not feasible for a gardener. As a gardener there are lots of accepted practices which dictate planting out "Warm Weather Crops" in spring, IMO these same practices and accepted Low / High Temperatures actually apply to successfully growing fig trees, for example Seed Germination Temperatures min - optimal - max with the associated time delays (increased time) caused by cool min temperatures.

            • PacNorWreck
              PacNorWreck commented
              Editing a comment
              jrdewhirst - I also want to point out that temps in the 50s aren’t noise for those of us in the PNW, they are extremely consistent, nightly events. The time spent dipping down into the 50s, and then back into the 70s or (sometimes / rarely) 80s / 90s here is time the plants spend less able to grow and photosynthesize. Nights are important, since plants are very active at night doing the actual conversion of sugars and nutrients into more tissue, and recharging their water supplies. Mornings, too, since our figs might not get into the “efficient” range (65+ or 70+) until halfway through the day.

              In any case, I am not sure we can separare the impact of heat from the impact of cold - cold is just the absence of heat after all.

            • jrdewhirst
              jrdewhirst commented
              Editing a comment
              PacNorWreck -- I take your point. My suggestion is not to ignore cold but to analyze the impact of heat using observations unimpacted by cold.

              Like, if you were measuring the performance of race cars using different fuels, you'd eliminate any tracks with potholes. That way, the presence or absence of potholes wouldn't distort your inferences about the performance dance of the fuels.

              Then if you really want to know the impact of potholes, you'd take some cars with OK fuels and subject them to tracks with different severity of potholes.

          • #11
            My suspicion is that it’s less a threshold and more a curve based on root and vascular activity at various temperatures. The plant’s activities accelerate as you move along the curve until you reach a certain maximum efficiency temperature, above which the plant starts to become less efficient.

            Every hour that can be spent closer to the maximum efficiency temperature is helpful, as the plant can convert sugars to growth, or photosynthesize, or move water and nutrients around more quickly. This would explain the PNW observation that our night temperatures slow down both fruit set and ripening - our trees are just spending more time doing things less quickly / efficiently because more hours are spent at cool + inefficient temperatures.

            This is well studied in citrus - maximim growth and fruit development occurs when roots are somewhere in the 80s.
            Attached Files
            Eric - Seattle / Zone 8b (Sunset Zone 5) - W/L: Bill’s “The One” / Stallion / Sturch, De Tres Esplets, Lampeira Preta, any very early berry fig

            Comment


            • Sod
              Sod commented
              Editing a comment
              Exactly. Like terminal velocity. To keep the plant generating at optimum efficiency it needs to stay at a certain temperature range, the height of the bell curve.

          • #12
            Cool nighttime temperatures above ~ 50 - 55°F are not typically problematic, its the Temperate and Light that produce actual photosynthesis during the daytime hours...

            The GDD for the examples are;
            Location: Temp D/N (1)
            July
            Temp (1)
            Aug
            GDD avg (2)
            July
            GDD avg (2)
            Aug
            Azores 75 / 64 77 / 66 19.5° 21.5°
            Providence 83 / 64 81 / 63 23.5° 22.0°
            Philadelphia 89 / 72 87 / 70 30.5° 28.5°
            Raleigh 90 / 70 89 / 69 30.0° 29.0°
            Portland 80 / 57 80 / 58 18.5° 19.0°
            Ulster, NY 82 / 63 80 / 62 22.5° 21.0°
            Notes:
            1. D / N = Monthly average of Day / Night Temperatures.
            2. GDD = Growing Degree Day Base 50 Average [ D + N / 2 - 50 = GDD ]



            2020 Ulster NY, GDD average per Month was;
            2020 Yr.
            Month
            GDD avg.
            Deg. Day
            Apr 0.2°
            May 7.6°
            Jun (S) 16.4°
            Jul 23.6°
            Aug 19.8°
            Sep (E) 12.1°
            Oct 3.3°
            Notes:
            1. S & E = Start and End of growing season Zone 5B, Ulster NY.

            2. GDD Calculator...https://www.greencastonline.com/grow...gree-days/home


            Edit;
            IMO, the above GDD info is useful for seasonal comparison and evaluations because several conclusions can be made from the available info and the OP info.
            The calculations account for Zone and Seasonal variations of Day and Night Temperatures.
            1. The range for adequate Spring time temperatures is ~ 15° to 20° day average (~ 65° - 70°F average).
            2. The range for adequate Summer time temperatures is ~ 18° to 30° day average (~ 68° - 80°F average).
            3. A value above 30° GDD ( > 90°F Day temps) is superfluous to growth and ripening of figs.
            Last edited by AscPete; 07-16-2021, 07:34 PM. Reason: Put calculations in Table Format and added Edit, some conclusions...
            Pete R - Hudson Valley, NY - zone 5b

            Comment


            • #13
              Sounds like we're talking about modified GDD where they put a cap on temperature, above which no additional value is gained. I haven't seen this for figs specifically but it is out there for corn.

              For corn the cap is 86F, the equation is the same GDD = Modified Growing Degree Day Base 50 Average = (D + N) / 2 - 50 ; but any D>86F is set to 86F.

              The OP question then would be, what is the top-level temp above which there is no increase in ripening speed? 86F like corn, or is it 80, 85, 90F? My data is useless here - hopefully someone in warmer climate can chime in.
              New Hampshire: z5b/6a. WL: DTE, Iranian Candy

              Comment


              • AscPete
                AscPete commented
                Editing a comment
                batty ,
                A tunnel would effectively change both Day and Night temperatures increasing your Daily and Total GDD.
                If GDD was increased to that of Commercial fig growing regions you could then probably ripen figs within those optimal time periods, its a given...
                That's why Commercial Greenhouses exist as multi-million dollar industries.

                The question is what's your current Seasonal (Start - End) and Daily GDD...
                You may be able to use this site to check / calculate GDD... https://www.greencastonline.com/grow...gree-days/home

                BTW, The quantity of days where a cap would be required are minimal and would only add at most one (1) week to the Fig ripening ‘Schedule’ in actual real life conditions. Low GDD value days are the norm, they increase the amount of time on the ‘Schedule’. Optimally it takes;
                Breba; 3 to 3-1/2 months to grow and ripen
                Main Crop; 3 - 5 months to grow and ripen, early to late ripening.
                These times have index values based on their location, your locations index values can be easily compared. The currently available index values for specific Fig cultivars are easily compared to a locations index values.
                Last edited by AscPete; 07-17-2021, 06:10 AM. Reason: Added BTW, for clarification..,

              • batty
                batty commented
                Editing a comment
                AscPete
                My in-season GDD50 are about 2400 average, approx 23 GDD average/day in July, overall very similar to yours in both heat and season length. I understand optimum varieties and timings for this location are more or less known.

                And you're correct in reality the cap in our climate is probably not significant.. but to the OP question, it could become quite significant in hot climates. If daily high averages 95+, the standard GDD50 equation may predict ripening times significantly earlier than reality.

                And I admit, I'm also just interested from an academic perspective.. I like maximum predictability.. down to the day, if possible

              • AscPete
                AscPete commented
                Editing a comment
                batty ,
                The 'error' would be at most 1 - 7 day in a typical ~ 5 month growing season, that works out to less than 5% which is a statistical equivalent...
                The question regarding the max and min temperatures can be answered by general plant physiology, photosynthesis 50° - 77° - 95° (min - max - min) and the Ficus carica L graphics and chart posted below... https://www.ourfigs.com/forum/figs-h...31#post1014231

            • #14
              This is a little OT, but given discussions above I thought I'd restate my concerns about Growing Degree Days (GDD) as a measure of cumulative heat for fig growers.

              Let's ask an illustrative hypothetical question. Grower A has 100 F days and 50 F nights. Grower B has 75 F days and 50 F nights. Grower A accumulates GDDs twice as fast as grower B. Do Grower A's figs ripen twice as fast? No, not nearly that fast.

              Most likely, these two growers have very similar growth and ripening. Grower B might even have an edge. The key issue is that above some point, extra heat produces diminishing returns. The arithmetic of GDD treats all degrees equally.

              Let's ask another illustrative hypothetical question. Grower A has 70 F days and 50 F nights. Grower B has 60 F days and 50 F nights. Grower A accumulates GDDs twice as fast as grower B. Do Grower A's figs ripen twice as fast? No, much faster.

              Most likely, these two growers have widely divergent results. Grower A will have reasonably satisfactory growth. Grower B mightn't get much growth -- or any ripe figs -- at all. The key issue is that below some point, diminishing heat produces increasingly adverse returns. But again, the arithmetic of GDD treats all degrees equally.

              Making this critique more concrete: In the 1st hypothetical, I'm Grower B -- more or less. I can ripen Ronde de Bordeaux (dormancy to ripe fruit) in 95 days. The GDD metric predicts that a grower in Saudi Arabia will ripen RdB in ~45 days, or maybe less. I don't think that's what happens.

              The reality is that every extra degree above some threshold (e.g., 75-80 F) has diminishing positive impact. The reality also is that ever extra degree below some threshold (e.g., 60-65 F) has diminishing positive impact. GDD doesn't reflect either the accelerating benefit of heat between roughly 50 and 75 F or the decelerating benefit of heat between roughly 85 F and anything higher.
              Joe, Z6B, RI.

              Comment


              • AscPete
                AscPete commented
                Editing a comment
                jrdewhirst ,
                The only problem with these hypothetical is that they completely ignore the know Ficus carica L Phenology which has specific time increments relative to seasonal ambient temperatures, the same ambient temperatures that can be index with GDD / accumulated temperatures.

              • jrdewhirst
                jrdewhirst commented
                Editing a comment
                Pete -- I don't get your point here. Can you elaborate?

              • AscPete
                AscPete commented
                Editing a comment
                jrdewhirst ,
                To answer your question review the diagrams and chart in the post below... https://www.ourfigs.com/forum/figs-h...31#post1014231

            • #15
              Originally posted by jrdewhirst View Post
              This is a little OT, but given discussions above I thought I'd restate my concerns about Growing Degree Days (GDD) as a measure of cumulative heat for fig growers.

              Let's ask an illustrative hypothetical question. Grower A has 100 F days and 50 F nights. Grower B has 75 F days and 50 F nights. Grower A accumulates GDDs twice as fast as grower B. Do Grower A's figs ripen twice as fast? No, not nearly that fast.

              Most likely, these two growers have very similar growth and ripening. Grower B might even have an edge. The key issue is that above some point, extra heat produces diminishing returns. The arithmetic of GDD treats all degrees equally.

              Let's ask another illustrative hypothetical question. Grower A has 70 F days and 50 F nights. Grower B has 60 F days and 50 F nights. Grower A accumulates GDDs twice as fast as grower B. Do Grower A's figs ripen twice as fast? No, much faster.

              Most likely, these two growers have widely divergent results. Grower A will have reasonably satisfactory growth. Grower B mightn't get much growth -- or any ripe figs -- at all. The key issue is that below some point, diminishing heat produces increasingly adverse returns. But again, the arithmetic of GDD treats all degrees equally.

              Making this critique more concrete: In the 1st hypothetical, I'm Grower B -- more or less. I can ripen Ronde de Bordeaux (dormancy to ripe fruit) in 95 days. The GDD metric predicts that a grower in Saudi Arabia will ripen RdB in ~45 days, or maybe less. I don't think that's what happens.

              The reality is that every extra degree above some threshold (e.g., 75-80 F) has diminishing positive impact. The reality also is that ever extra degree below some threshold (e.g., 60-65 F) has diminishing positive impact. GDD doesn't reflect either the accelerating benefit of heat between roughly 50 and 75 F or the decelerating benefit of heat between roughly 85 F and anything higher.

              In your hypothetical B you are describing Seattle nearly perfectly, and we do in fact ripen much more slowly than nearly anyone else in the country. Mt Etnas are not a given for us in every summer - only your RdBs, improved celestes, etc - and even then, our quality can’t come close to someome like Evdurtschi who is not in a scorching hot climate, per se, but just has plants spending more time in the optimal range above 70, and much warmer evenings than we experience.
              Eric - Seattle / Zone 8b (Sunset Zone 5) - W/L: Bill’s “The One” / Stallion / Sturch, De Tres Esplets, Lampeira Preta, any very early berry fig

              Comment


              • AscPete
                AscPete commented
                Editing a comment
                PacNorWreck ,
                I'm also in that B group, except that I have two (2) months, July and August were the night time temps average above 60°F (24° - 19° days). With a total Season GDD of ~ 2400° I'm only able to ripen ~ 50% of my Mount Etna type Mid-Season Ripening Fig crop and no Late Season Main Crop figs without season extending Practices or Structures (Shuffling or a Hoop House / Greenhouse).

              • Sod
                Sod commented
                Editing a comment
                I’m in the same boat as you Pete. The difference being we rarely get nights in the 60s here. I think last year my total GDD was ~2400

            • #16
              jrdewhirst
              Your first hypothetical shows exactly why the top temperature cap I had mentioned is used. Then GDDs are not excessively counted above e.g. 86f

              The 2nd hypothetical, I think, could be improved by using a higher, low threshold e.g. GDD 60, where 60 is the base instead of 50.

              Still, obviously not perfect, it would still count 80f as double 70f, and it counts nighttime temps as equally important as day temps.. none of which is exactly true. But it gets closer.

              I actually like your simpler model of X days above a temp threshold. The challenge seems to be incorporating the drag of low overnights, and more moderate days that may be just below the threshold X, but may count for something.

              Can you point me to the community dataset you had mentioned? I'm curious to take a look.

              New Hampshire: z5b/6a. WL: DTE, Iranian Candy

              Comment


              • #17
                << Your first hypothetical shows exactly why the top temperature cap I had mentioned is used. Then GDDs are not excessively counted above e.g. 86f

                The 2nd hypothetical, I think, could be improved by using a higher, low threshold e.g. GDD 60, where 60 is the base instead of 50.

                Still, obviously not perfect, it would still count 80f as double 70f, and it counts nighttime temps as equally important as day temps.. none of which is exactly true. But it gets closer.

                I actually like your simpler model of X days above a temp threshold. The challenge seems to be incorporating the drag of low overnights, and more moderate days that may be just below the threshold X, but may count for something.

                Can you point me to the community dataset you had mentioned? I'm curious to take a look.
                >>

                I think we're in total agreement. A temperature cap ameliorates the problem at the high end. A floor ameliorates the problem at the low end. But I say "ameliorates" rather than "cures" deliberately. As you say, "it gets closer."

                Pete seems to suggest (comment above) that the cap could be at 90 F or even 80 F. He writes: << IMO, "A value above 30° GDD ( > 90°F Day temps) is superfluous to growth and ripening of figs." As proven by figs ripening properly at 20° - 25° GDD's in Commercial Fig Growing Regions... >> As 25 C = 77 F, this seems to imply that the GDD cap could be as low as 77 F; and as 20 C = 68 F, it implies that the floor could be much higher than 50 F.

                So as you suggest, the implication is a GDD measure with a floor at ~60 F and a cap at ~80 F.

                But as you also correctly point out, this still implies that an 80 F day is twice as good as a 70 F day, which it definitely isn't -- they're probably roughly equal. And it also implies that a 70 F day is twice as good as a 60 F day, which it also definitely isn't. It may be 5x as good. So even in the range between the floor and cap, the function is non-linear with the floor and cap serving as asymptotes. The growth "dial" seems to go from fully OFF to fully ON fairly rapidly right around 65 F.

                That's why I settled on the simple day count, which I later elaborated into an hour count. The best measure I found was a cumulative sum of daylight hours >65 F. That isn't exactly correct either, but it is even closer. Your caveats re (1) the negative impact of cold nights, and (2) the positive impacts of sub-threshold days are totally right. I'm just hoping to walk before I try to run. And the GDD measure doesn't address those problems either.

                PM me an e-mail address and I'll send you the spreadsheet of data.

                One final point. The purpose of this thread was to address the question, "Does high heat matter?" This discussion of metrics is a digression. But if we can just take away Pete's observation that figs ripen just fine for commercial growers at 68-77 F (which is basically the temp range in the summer in the Azores), I'd be happy.
                Last edited by jrdewhirst; 07-17-2021, 10:39 AM.
                Joe, Z6B, RI.

                Comment


                • #18
                  jrdewhirst , batty ,

                  Click image for larger version  Name:	Fig Research Tunisia.png Views:	0 Size:	200.7 KB ID:	1014233

                  Weather Data... https://weather-and-climate.com/aver...sousse,Tunisia
                  Ficus carica Paper... https://doi.org/10.1016/j.sajb.2020.04.020
                  You may only view thumbnails in this gallery. This gallery has 2 photos.
                  Pete R - Hudson Valley, NY - zone 5b

                  Comment


                  • jrdewhirst
                    jrdewhirst commented
                    Editing a comment
                    AscPete --

                    Yeah, I get the arithmetic. I just see no need to stick with GDD50 if evidence suggests that some other variation might perform better. So (1) if there is no or minimal fig growth below 60 F, then it makes sense to raise the floor to 60 F. And (2) if the growth rate plateaus above 80 F, then it makes sense to set a cap at 80 F.

                    So while GDD50 is directionally correct, I'm suggesting ways that it can be improved. For many growers, these supposed improvements may not matter. But for the grower with lots of hours between 50 and 60 F or lots of hours above 80 F, the modification might help.

                    Said differently, a measure like GDD60/80 might reduce the variance around the medians you calculate to reflect fig phenology.

                    << metabolic processes aka Growth don't stop, which is why a "CAP" is not necessary >>

                    A cap on GDD does not imply that growth stops. It implies that the rate of growth stabilizes. [Growth stays positive, but the 1st derivative drops to zero.]. So for example, a cap at 80 F implies that growth is the same at 80 F as 90 F or 100 F. Of course, the truth may well be that growth decelerates at very high temperatures, which would imply negative degrees. But I'll wait til we know more to suggest that tweak.

                  • AscPete
                    AscPete commented
                    Editing a comment
                    jrdewhirst ,

                    I disagree with the 60°F base because growth occurs down to ~ 50°F, we are using max to min daily temp average ("swing").
                    The max number is debatable for warmer zones / regions, it should be closer to 90°F due to the same temp "swing / spike" it's not a "12 hour maintained" 50° or 90°F...

                    I absolutely prefer GDD Base50 because its almost universal in its use and is easily calculated by almost everyone.

                  • jrdewhirst
                    jrdewhirst commented
                    Editing a comment
                    I see your point re the ease of use of the GDD number. But if we're going to recommend this measure, then I'd prefer to note the shortcomings, e.g., "This is easy to use and good enough for most purposes. But if you want to fine-tune your expectations regarding fig performance in your garden, then . . . "

                    Yes, I agree that some growth may occur below 60 F. Given the paucity of data, it's a judgment call whether we'd get better prediction of fig ripening by ignoring time spent under 60 F. If you live somewhere warm, it probably won't matter. If you live somewhere with lots of days with a peak temperature between 50 and 60 F, it could matter a lot.

                    And, yes I agree that growth occurs above 80 F. The question is whether growth is materially faster at 90 or 100 F than at 80 F. I haven't seen any evidence that it is faster. Your own observations about optimal temperatures and commercial growing practices suggest that growth is not faster at high temperatures than at "optimal" temperatures. So I think the better approach is to use a measure that assumes stable, high growth rates at high temperatures. Note: An uncapped GDD50 measure implies that growth is twice as fast at 100 F than at 75 F. This is patently false.

                    I don't want the perfect to be the enemy of the good. GDD50 is easy to calculate and quite acceptable for most growers. But it seems clear to me that a refined measure with a higher floor (55-60?) and a cap (80-90?) will produce more accurate predictions of ripening for those in either cool or hot growing areas.

                • #19
                  I’m late to this discussion but can share some numbers since I grow year round in a greenhouse with a temperature recorder. My greenhouse gets pretty hot but my ripening numbers aren’t better than those posted at the start of this thread.

                  Main crop thus far:

                  Improved Celeste (ICON)
                  • Bud break: 2/27
                  • First main crop figlets: 4/9
                  • First breba harvested: 5/26 (only one)
                  • First main swelling: 6/19
                  • First main harvested: 6/26
                  • Days from fruit set to harvest: 78

                  RDB:
                  • Bud break: 3/5
                  • First main crop figlets: 5/3
                  • First breba harvested: none
                  • First main swelling: 7/5
                  • First main harvested: 7/10
                  • Days from fruit set to harvest: 68

                  Chicago Hardy
                  • Bud break: 2/26
                  • First main crop figlets: 4/8
                    First breba harvested: none
                  • First main swelling: 7/8
                  • First main harvested: 7/13
                  • Days from fruit set to harvest: 96

                  Florea:
                  • Bud break: 3/22
                  • First main crop figlets: 4/23
                  • First breba harvested: 6/1 (tree had tons of breba which I suspect slowed down the main crop)
                  • First main swelling: 7/10
                  • First main harvested: 7/14
                  • Days from fruit set to harvest: 82

                  Eastern Brown Turkey
                  • Bud break: 2/22
                  • First main crop figlets: 4/25
                  • First breba harvested: none
                  • First main swelling: didn’t record this.
                  • First main harvested: 7/15
                  • Days from fruit set to harvest: 81

                  Celeste
                  • Bud break: 3/9
                  • First main crop figlets: 4/12
                  • First breba harvested: none
                  • First main swelling: 7/14
                  • First main harvested: 7/17
                  • Days from fruit set to harvest: 96

                  Mary Lane Seedless
                  • Bud break: 2/26
                  • First main crop figlets: 4/12
                  • First breba harvested: none
                  • First main swelling: 7/9
                  • First main harvested: 7/14
                  • Days from fruit set to harvest: 96

                  Little Ruby (moved outside of GH after main crop set):
                  • Bud break: 2/28
                  • First main crop figlets: 4/9
                  • First breba harvested: none
                  • First main swelling: 7/10
                  • First main harvested: 7/13
                  • Days from fruit set to harvest: 95
                  Pics from the temp recorder are attached.

                  -Steve
                  Attached Files
                  Steve, zone 7a MD

                  Comment


                  • crosshairs
                    crosshairs commented
                    Editing a comment
                    @jrdewhirst
                    I consider myself a noob, both in terms of greenhouse-growing and (to a slightly lesser extent) figs. I’m much more proficient at taking notes than interpreting them. :-) But happy to share my thoughts anyway.

                    RDB and EBT are among 6 in-GH varieties that took over 55 days to go from bud break to fruit set (out of 15 total varieties). I can’t find a common thread between those 6 except that these are varieties that typically don’t set fruits their first few nodes. Maybe that sets them back a bit, I dunno. The other 4 in that group are Smith (60 days), CDDB (63), CDDG (60), and an unk I’ve never fruited so I can’t infer anything from it (57). FWIW these are 2nd year trees except RDB (3) and EBT (6, my oldest tree). Also RDB was in a shadier spot within the GH, and next year will be given more light exposure to see if that helps reduce the delay.

                    As for the 4-6 week gap, maybe high heat is a factor. I hadn’t really considered that. I also suspect lack of light is at play. I woke the figs pretty early in the season when nights were still long (and cold). I suspect it’s easier to wake figs than to ripen them.

                  • jrdewhirst
                    jrdewhirst commented
                    Editing a comment
                    crosshairs -- I didn't think of this before, but as soon as I read "noob" I realized that I should ask the age of the trees. I wouldn't expect 2nd year trees to fruit as quickly as mature trees. And I'm not so sure about a 3rd year RdB "in a shadier spot" either. Shade would be an issue generally -- what is causing it? Are the trees crowded? Do trees on the south side shade trees on the north side?

                    I'm not convinced that day length is a factor. By March, you've got 12-hour days. For a greenhouse in sun that should be enough.

                    I also don't think whether a fig normally fruits at the first few nodes is the answer. My experience with RdB and Smith doesn't suggest any lag in fruit-set.

                    So I'm left with (1) the age of the trees, and (2) the heat of the greenhouse. Plus maybe the amount of sunlight hitting specific trees.

                  • crosshairs
                    crosshairs commented
                    Editing a comment
                    jrdewhirst - I reckon you may be right. Re: light, it is crowded in there as I trial varieties to see what makes the cut. Next season it should be more open and light (and age) should be less of a factor.

                • #20
                  crosshairs some really good info there! Thanks!
                  Travis - Cincinnati OH. Zone 6
                  wishlist- zaffiro, figoin, cddb,

                  Comment


                  • #21
                    Lots of good info guys.

                    During growing season my goal for heat is to keep my figs as close as possible to a constant temperature of 25 Celsius to 77 Fahrenheit or a little higher
                    Toronto, Canada USDA Zone 5. Wish List: Smith and Improved Celeste. I'm always interested in trading cuttings if your in the Southern Ontario area. Thank You!

                    Comment


                    • #22
                      Bravo_Figaro Do you use a green house to maintain that temperature? (a true newbe)

                      Comment


                      • Bravo_Figaro
                        Bravo_Figaro commented
                        Editing a comment
                        I do. As soon as spring starts I try to get all my fig started with a head start then slowly transition them outside

                    • #23
                      Other than greenhouses is there a way for those of us that grow figs in areas that typically get night time temperatures in the 50's retain the approximate optimal daytime heat overnight? Covering? Reflective surface? I appreciate all the efforts being put forward to help understand the nuances as this gives us information regarding specifics. Now that I understand a bit, I want to try something that I maybe able to modify in my area🙂

                      Comment


                      • jrdewhirst
                        jrdewhirst commented
                        Editing a comment
                        I'm not trying to chase you away, but you might get a better response off you start a new thread focused on your question.

                    • #24
                      There is an assumption, but there is no actual data on timing: another, opposite, effect of a normally-high temperature on the rate of development and ripening of figs is possible, - with regular and abundant watering, the appearance and development of inflorescences and, possibly, ripening of fruits are slowed down due to the rapid growth of vegetative the mass of plants and the elongation of internodes. And at a VERY high temperature, the physiological state of plants is close to dormancy (forced), the growth of shoots stops, but there is no information about how this affects the phases of development and ripening of fruits. It seems to me that extreme conditions for photosynthesis and shoot growth may be normal for fruits in the last stage - with a change in color and subsequent softening.
                      Андрей. N.-W. Кавказ, пень Абрау, 7б-8а

                      Comment


                      • AscPete
                        AscPete commented
                        Editing a comment
                        There's lots of data based on Horticultural Academic Research being done on Ficus carica L, with emphasis on Cultivars, Plant Nutrition, Water, Temperature, Sunlight, Plant Spacing, Etc...
                        Its accepted (Proven) that Photosynthesis has an optimal temperature range, current Ag Research in Arid Fig Growing Regions is now looking at "Shade Houses" to mitigate the increased heat caused by Global Climate Change.

                      • acerpictum
                        acerpictum commented
                        Editing a comment
                        AscPete Thanks for The Fig: Botany, Horticulture, and Breeding - a lot of great information and it's in a concise form!

                      • AscPete
                        AscPete commented
                        Editing a comment
                        You're welcome.

                    • #25
                      Ficus carica L Phenology is "set in stone" the growth and ripening is their Genetic "Nature" not Nurture...
                      The "Timing" cannot be dramatically changed...

                      Older Topic... https://www.ourfigs.com/forum/figs-h...-ripening-figs

                      Phenology; ... http://figs4fun.com/Links/FigLink129.pdf

                      Breba Figs; 3 to 3-1/2 months:
                      Stage I ... Spring growth to quiescence, 7 - 8 weeks
                      Stage II ... Quiescence stage (or stagnant stage) 2 weeks.
                      Stage III ... Ripening 2 weeks.

                      Main Crop Figs; 3 to 5 months / early to late ripening:
                      Stage I ... Rapid growth to quiescence, 5 - 6 weeks
                      Stage II ... Quiescence stage (or stagnant stage) 3 - 8 weeks (depending on the fig variety)
                      Stage III ... Ripening 3 - 5 weeks.


                      The "Optimal" conditions at UC Riverside, California. Seasonal GDD (base50) and mean average temperatures as follows;
                      (assuming a March 1 season start date)... https://www.greencastonline.com/grow...gree-days/home
                      2017 Season:
                      1458° - 3 months, Early and Breba (Mar - May, 90 days 66°F avg)
                      2249° - 4 months, Middle (Mar - Jun, 120 days 71°F avg)
                      3311° - 5 months, Late (Mar - Jul, 150 days 76°F avg)

                      1735° - last 2 months, ripening stage 2 & 3 (Jun - Jul, 60 days 79°F)


                      The preliminary info from calculating the statistical median GDD (base 50) of fig ripening dates indicates;
                      Preliminary Fig GDD values... https://docs.google.com/spreadsheets...zD4/edit#gid=0 ;

                      GDD(50) - Season:
                      1500° - Breba crop ripens
                      1600° - Very early ripening main crop
                      2000° - Early ripening main crop
                      2500° - Middle ripening main crop
                      3000° - Late ripening main crop
                      Pete R - Hudson Valley, NY - zone 5b

                      Comment


                      • acerpictum
                        acerpictum commented
                        Editing a comment
                        Is this averaged over several years?

                      • AscPete
                        AscPete commented
                        Editing a comment
                        acerpictum ,
                        UC Riverside (Ira J. Condit) and UC Davis have been doing Ficus carica research for decades... http://figs4fun.com/The_Fig_by_Ira_Condit.html
                        Volcani Center, Bet Dagan 50250 Israel has been around for 100 years, no idea how many in Ficus carica research.

                      • jrdewhirst
                        jrdewhirst commented
                        Editing a comment
                        AscPete -- We've had this conversation before, so you're gonna feel like it's Ground Hog Day. I'm sorry, there's stuff here that I STILL don't get or, if I do get it, don't agree with.

                        1. Note that the linked paper on Phenology never mentions the word. So it's tough to figure out what's relevant.

                        2. The "optimal" conditions at UC Riverside seem to be just a description of the conditions there. How do we know that those conditions are optimal? The link is merely a GDD calculator.

                        3. The data at the end represent the "statistical median." That's all fine -- it represents some genetically driven central tendency, estimated over the sample analyzed -- but there is wide variation and that's what I'm focused on.

                        GDD(50) - Season:
                        1500° - Breba crop ripens
                        1600° - Very early ripening main crop
                        2000° - Early ripening main crop
                        2500° - Middle ripening main crop
                        3000° - Late ripening main crop

                        For example, look at the results for main crop figs ripened on a potted RdB. Tony (@mountainfigs) in mountainous WV ripened a first fig after 1883 GDD (and I ripened a first fig in cool RI after 1958 GDD); whereas mgginva in Virginia ripened a first fig after 2565 GDD. For forum newbies, both of these other growers are/were very reputable. Even accounting for the possibility that one may have picked figs less ripe than another, this says to me that the 36% extra heat in VA did not accelerate the ripening of RdB. The GDD measure accumulates that excess heat. Growers in hot regions whose expectations are set by GDD standards will be surprised that their figs take so long. Growers in cool regions may be surprised that their figs ripen so early, again relative to GDD standards.

                        p.s. This is exactly the same dataset I used for my own analysis, which led me to start counting hours/days >65 F.
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