Hanging from your oak tree are what appear to be tiny green apples. Unfortunately, they're not edible. Fortunately, they're fascinating. Oak apple galls form when a tiny gall wasp lays an egg in developing oak tissue. The tree responds by growing a round protective chamber around the larva, creating the familiar "oak apple." These galls start out green and soft before drying into brown papery spheres. While they may look alarming, they're mostly harmless and rarely cause sign