In order to produce the most fruit, apple trees need another apple tree, preferably a different variety of apple, with which it can exchange pollen. This process is known as cross-pollination. Both bees and the wind serve to transfer pollen between trees. Trees intended to cross pollinate each other must bloom at about the same time in order for the exchange of pollen to take place. Honeycrisp is one of the first apple varieties to bloom in the spring, so it needs pollinators that also bloom at about the same time.
The bright crimson apple is a cross between Jonathan and Wagener, developed in Idaho in 1935. The flesh is green or pink tinged. Idared apples mature in late September or early October.
The Jonafree apple was developed in Illinois in 1979. Jonafree trees produce a large quantity of bright red fruit. Jonafree apples can be harvested in mid-September and keep well.
Jonathan apples have been cultivated since before the Civil War. The red-tinged fruit of Jonathan apples is crisp and mildly acidic. Jonathans are harvested in October. The trees are known to be heavy producers.
Empire apples were developed in 1966 from a cross between Red Delicious and McIntosh. A dark red apple with very white flesh, Empires are prized for desserts and cider. Empire apples are harvested in September.
Liberty apples are similar to McIntosh, good for pies and cider. Liberty apple trees are very disease resistant. They're harvested in October.
Manchurian Crab Apple
Crab apples can successfully cross-pollinate apple trees. Manchurian crab apples are a type of Siberian crab apple tree. They're very cold hardy and planted as ornamentals, producing large white blossoms in spring. The fruit is pea-sized and attracts birds and wild life.