"Pip" means the seed of an apple (Malus domestica). A simple way to view the pips is to cut an apple in half, revealing the tough core that houses varying numbers of seeds based on the type and the health of the parent plant. A single apple seed, however, rarely produces the same type of tree from which it was grown. Most apple trees today are hybrids, or crosses, of at least two other types, with the focus placed on developing more disease-resistant or more productive varieties. Pips must undergo a cooling period in order to germinate properly.
Cool Your Pips
Hardy in U.S. Department of Agriculture plant hardiness zones 3 to 8, apples are grown from pips that have been chilled at a steady temperature of 40 degrees Fahrenheit during a period of dormancy that is also called after-ripening. This subjects the pips to the same conditions they would experience if left outside during the winter. In fact, planting the seeds outside in the fall is one way to accomplish the after-ripening, during which the seed's embryo develops fully and becomes capable of producing new growth. The other method involves refrigerating the seeds for a specific time before planting them.
According to the University of Minnesota Extension's website, fruit trees sold commercially are grown using root stock and scion, plus a secondary variety stock that is grafted onto the root stock. If you plant apple pips -- after the chilling process -- it takes another six to eight weeks before they germinate.