A person on a different website said it's a 1:6 ratio, which I'm sure is true, but does the '6' mean 6 'value', as in they can harvest 6 crops worth 1 food each or 12 crops worth .5 food each? Or is it just 6 plants, and however much food it provides doesn't matter?
According to the Wiki:
A single settler assigned to harvesting food can work 6 food units worth of crops, whether they're the standard 0.5 units per plant or mutfruit's 1.0 unit per plant.
This means that they can work 12 crops at .5 each, or 6 at 1 unit each (or a mixture).