The majority of apple trees require cross-pollination with another variety of apple or crabapple tree to bear fruit. Even those apple tree varieties that are self-pollinating will produce better fruit with cross-pollination. The key to finding a suitable pollinator to pair with your tree is choosing an apple tree variety that blooms at the same time.
Early blooming varieties of apple include Idared, Liberty, Empire, Red Delicious and Honeycrisp. See Resources for a full chart of all varieties cross-referenced with their suitable pollinators. Plant any of these varieties in a grid configuration for successful cross-pollination between them. The pollinators can be placed in alternating rows with your apple trees or staggered among the rows for good coverage. Remember that bees are your chief pollinators, so avoid insecticides during the blooming periods to avoid harming them.
Mid-season bloomers include Gala, Golden Delicious, Granny Smith and Braeburn. The Red Delicious variety may also fall into this group as it can bloom from early to mid-season. The Manchurian crabapple also makes a good pollinator for mid-season bloomers.
Late-blooming varieties of applies include Enterprise, Golden Rush and Rome. The Granny Smith variety is also one that is on the cusp between two blooming times and could be used mid-season or late-season. The Snowdrift crabapple is a possible pollinator or late-season bloomers.
Some varieties of apples are sterile and cannot be used for pollination with any variety. These include Jonagold, Winesap, Stayman and Mutsu.