My guess would be drought incuced hardiness.
The pots are 1ft away from a running stream, where the ground never dries, and I nestle every pot a couple inches down into the ground so that osmosis will keep them ambiently moist, so that I almost never have to water (except maybe when fertilizing).. I considered that thought at first but.. there has definitely not been a recent drought or a 'localized' drought in any of those pots.
It rained a bunch before these freezes anyway..
This is indeed a "thing," and has been seen in citrus and lychee. Why not mango? If you read the history of the Pickering mango, it was originally selected by the Zills because of apparent cold hardiness after a freeze in south Florida. However, mature trees did not vary significantly in hardiness from other mango trees.
I did see a video where Zill mentioned that, but I did not know the apparent colder hardiness was only relevant to his original tree as a young sapling.
However I must ask, did the
original* Pickering not display superior cold tolerance when it got bigger, or was it grafted* Pickerings that did not display superior cold tolerance when they got larger?
Maybe turpentine and other r/s's promote less cold hardiness when grafted.
Maybe enhanced 'wind wicking' caused the supposed decrease in hardiness as the tree got larger? (assume what's in bold is true)
While it might be possible to select for hardier mangoes, you can't select for genes that are not there. Mango leaves are used cerimonially in India and have been grown for centuries (if not milenia) in areas colder than their typical adaptation. I would assume that if a hardier tree exists, it is most likely to be found in India. I am skeptical (although on can't entirely rule out the possibility) that we in the US will achieve something in a few years that has not been done in India over the thousands of years that mangoes have been grown there.
Very true! Curious if the USDA or any other ag organization has/had sent experts out to Asia to document or 'discover' potential anomalies like this (in reference to, at least, mangos)? I know Brewster scoured the extent of the lychee range (<--supposedly but I doubt actually obtained & brought back the cold hardiest ones. He should have brought back 'sour, mountainous, more hardy (did Swingle comment this?)' marcotts, if not for fruit then at least for future breeding projects. Ugh), but I'm not familiar with any other explorers who had a similar mission as Brewster..
Did Swingle and his explorer colleagues ever consider this 'agenda', or were they only sent out to bring back generalized, potentially-commercial species that the US didn't have at the time?
(basically meaning, were they not too concerned with aquiring subvarieties on the extremes of temperature tolerance spectrums and such?)
