4 Years of Potted Figs in a GH during the Springtime - Some GDD Observations

The trees this year woke up anywhere between March 1st and the 25th. There are always stragglers and still are, but because of less clutter inside the GH this year, most are showing very small figlets only 3 weeks after breaking dormancy (no pinching). I fed them minimally and they really only get 4-5 hours of sun. It is crowded in there, so some get even less, which continues my belief that heat units are immensely important to get a fig tree to bolt (flower). Starting in mid February, I consistently kept temps above 50 at night. There can be quite a range during the day, but the heater stops at 60F and a sunny day is enough to boost temps by at least another 30F. We probably had 10 days around 90F in there during that 3 week period.

Before I go further, I want to note that if temperatures are too high in the GH too soon, the trees bolt very quickly and what happens is that energy is then being spent towards fruit formation therefore lowering vigor. As a result some trees have had a very early fruit set, but lower overall production. It’s probably a better practice to have the heater turned off during the day when temps hit 50F to delay the number of days at 90+. I can see this being somewhat of an issue in places with very warm springtime temps. Even the CDD figs like Blanc, Grise, Noire & Roja are showing fruit only 3 weeks after waking from dormancy. Therefore it's not hard to imagine that in these climates classifying figs as early, mid or late would differ significantly from someone in a much cooler part of the country.

I see a lot of value in two separate GDD calculations. One for the growing degree days required to set fruit. The other for the total required for maturation as it stands currently. I’m sure we can agree that varieties differ in the amount of heat units that they require to bolt, but anecdotally I’ve found that the bolting of specific varieties can be greatly impacted by doses of high temperatures ranging from 80-100F. Take Azores Dark for example, it's probably not as early as I once thought. It appears that it requires a much lower amount of heat units, but also gets kicked easily into fruiting mode when exposed to high temperatures. This could happen only 2 weeks after waking from dormancy. You could make an argument that the GDD calculation as it stands is all that's necessary. However, if you give all of your varieties temperatures consistently in that 80-100F range, they'll look like they're all going to ripen roughly at the same time because they’ll get triggered into fruiting around the same time. It'll be more difficult to discern from early, mid & late varieties as I mentioned in the above paragraph. For example I have figs like VdB setting fruit the same time as my Coll de Damas when we know that the CDDs are late to ripen and VdB is a mid season ripener. Again, you would see this occur as well in a climate with very high springtime temperatures. This is why I believe ripening dates for example in Majorca, don't always translate well over to the northeast.

A few more examples, I've also noticed that figs like Black Madeira & Dels Ermitans bolt easier than most late ripening varieties. However, after formation they take longer than your standard 90 days to ripen making a good case for data on the required amount of heat units before and after fruit set. A different story seems to be explained by the Coll de Damas. Like Azores Dark, they seem to react strongly to temps in the 80-100F range, but the difference here I think is that they require a much higher number of days at those high temps before setting.

As a whole I estimate that I’ve had the pleasure of what it would be like growing figs in a climate much warmer than my own and I very much so recommend getting some form of plastic over top of your fig trees in the spring. Even a low tunnel without supplemental heating can be very beneficial. They’re very easily set up and taken back down, they’re not a big eyesore and are quite affordable.

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