How to tell sweet and pie cherries apart? The fruit are easy, if you take a bite. In my experience, wild sweet cherrt fruit are also quite dark in color. The bark of mature trees helps too. This sweet cherry in another preserve (nature preserve, that is) near Ives shows the frequent pattern, almost like a birch. Sour cherries are usually more scaly. The flowers of sweet cherries have sepals with smooth edges. Sour cherries are toothed. Sweet cherries are not as frequent as sour. That's because sweet cherries can only be pollinated by trees from a different tribe. Closer relatives usually don't work. Most of the garden varieties of cherry, like Japanese or weeping, are derived from this species.