Whenever I see that, I always wonder if the species has been fully
explored in it's original range. I can't help but wonder if there were
plants growing in more challenging parts of the range that should be
found and brought out. For instance, Pyrus betulafolia is often
considered a somewhat cold tender rootstock for pears. But if you
check, you find that the main stock was from material collected at the
southern edge of it's range, and there are much hardier forms of the
same species farther north. I can't help but wonder if there aren't
some forms of Chilean Guava that are hardier than what is commonly
sold. It's one of the things NAFEX can do well - look for forms of
fruits that grow outside the normal range of any given species.
-Lon Rombough