If you are doing a study of apples, or on trees in general, you should really consider using the book, The Apple Pie Tree, by Zoe Hall. This wonderfully illustrated book follows a single apple tree, and the two girls who love it, through the seasons, until its fruit can finally be picked, chopped, and baked into a perfect apple pie. It is a great illustration of the cycle of seasons, as well as the process of making pie!
Understanding the cycle of seasons is a pretty obvious science objective, but learning to put things in an ordered series also builds cognitive and language skills that lay the foundation for reading and writing (beginning, middle, end) while also contributing to preschool math and problem-solving skills.