When are green apples the most sour?

I would guess that green is not as ripe as red and if you give the green ones time they will become red and sweet.

I would also guess that the flavor of green apples is sour because it’s a different type of apple.

If either is true then I would guess that the more sour it is, the less ripe it is.

It’s the type of apple. You’re most likely to find apple trees with small green fruit in your backyard. The sweeter apples originated in Central Asia, and were did not become popular in America until the nineteenth century, because until then apples in America were generally used for making cider, not for eating. (That’s what Johnny Appleseed planted his apple trees for.) Since apples reproduce sexually, so that every seed in a single apple contains different genetic material, apple trees planted from seed will produce somewhat unpredictable fruit, which is why most of the apples you buy in the supermarket are all the same, as the apples used on commercial orchards are not grown from seed, but are grafted from other trees.