Pollination occurs when pollen is transferred from one blossom to another. Apple trees require pollination in order to produce apples. Cross - pollination is when pollen from another variety of apple trees is needed for the apple tree to produce fruit. If a tree requires cross - pollination it is called self - unfruitful or self - sterile. If it does not need cross - pollination, it is called self - fruitful, self - fertile or self - pollination. Apple trees can be either self fruitful or self - unfruitful. There are some Apple trees that do not need pollination. Most Apple trees require cross - pollination from another variety of apple tree to set fruit. Red Delicious apple trees require a cross - pollination cultivar to bear fruit. If you want your red delicious apple too set fruit you can choose from many compatible cultivars. If you pair two or more of the following mid to late season apple trees Joanthan, Red delicious, Golden Delicious, Granny Smith, Fuji, York, Gold Rush, or Rome. You will have wonderful apples.