It can be confusing to determine when your apples are ripe--especially because there are so many different varieties of apples and each has a specific maturity time. While the best way to determine apple maturity is by keeping track of the time since the apple tree flowered and knowing the specific maturity times of an apple variety, you can also get an idea of apple ripeness by observing clues in the ripening apples.
Observe the color of the ripening apples. Whatever the color of the apple, according to the Oregon State University Extension Service, each apple variety will exhibit ripening clues with color changes. Yellow apples will turn from green to a full yellow when they are ripe. Examine blush apples (apples with variegated stripes) in the places where the apples are a lighter color. These areas will turn from green to yellow when they are ripe. You must check the inner flesh of red apples. When the flesh turns from green to white, these apples are ripe.
Pick an apple from a tree to determine maturity. If the apple releases easily as you twist it off, the apple is mature. If the apple resists your twisting, it is probably not ripe yet.
Watch for apples to start dropping from the tree. When you begin to find apples on the ground, choose one and examine it. If the apples on the ground are ripe, you can safely assume that more apples on the tree are ripe as well.
Cut into the apple and observe the juiciness of the flesh. Taste the apple. If it tastes pleasantly juicy and sweet, the apple is ripe.