From what I've learned: Some winery's use the "wild" yeasts that are
naturally on the grape. But after you learn about how they tend the
vats and vines you start to think the yeasts are not really "wild."
First, they ferment in the same building that has been used for years,
then they dump the spent lees and pressed grapes (pressed after
fermentation) back out in the field.
Makes you wonder just how wild those yeasts really are if they can
depend on them to produce the same wine season after season.