Draw a diagram for your notebook. Measure the circumference of different apple varieties. Cut it open and count them. This can be set up to measure any number of apple related things. Take a survey of favorite apples and graph them.
Younger children can practice lining up apples from smallest to largest.
Take a field trip to an orchard. Try to go when they are sorting, sizing and making apple cider. Dip in paint and press onto paper. Use some of the apple seeds to decorate the page. You can do this a couple of ways.