lorax

Personally I haven't done this (I live in the tropics), but I have a friend in Oslo who's growing the standard papaya's highland ancestor Vasconcellea cundinamarcensis (hardy to Z10) outdoors in pots. He overwinters them in his garage.

I have eaten V. cundinamarcensis fruits, and they're remarkably similar to "regular" Carica type papayas.

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I speak for the trees.