Apples grow from the flowers that bloom on an apple tree in the spring. For a flower to develop into an apple, the pollen that is produced by one flower must be transferred to another flower. Cross-pollination occurs when pollen is moved from the flowers on one apple tree to the flowers on another. This most often happens when bees come to the apple flowers to collect nectar and pollen and fly from one tree to another. Though an apple tree may produce some fruit without cross-pollination, it will yield a lot more fruit if cross-pollination occurs. This is why an orchard can't be made up of only one apple variety. At least two different kinds of apple trees are needed for cross pollination.
Some apple trees bloom much earlier
than others. Usually, apples that produce ripe fruit early in the season
are also early bloomers while those that fruit later in the season also
bloom later. It is helpful for cross-pollination to plant apple varieties
that bloom at the same time near each other in your orchard. Also, pollination
is helped by not planting two trees of the same variety next to each
other. Instead, alternate varieties in your rows. See the links below
for more information.
Pollination of Tree Fruits
Pollination of Apples by Honey Bees
Pollination of Apple Trees and Blooming Seasons
Pollination of Apple Trees