Cultivar Selection

• Although sour cherries do not require a cultivar for cross-pollination, introducing a second sour cherry variety can increase fruit production. If you want to grow sweet cherries, it is important to know that some cultivars do not cross-pollinate. Purdue University Cooperative Extension, which has published a chart that indicates which cherry cultivars are cross-incompatible and unable to fertilize other sweet cherry trees, compatible cultivars flower during the same period of the growing season to increase pollination.
  
  

How Many Cultivars Do You Need?

• At minimum, Purdue University Cooperative Extension recommends two sweet cherry cultivars for cross pollination. Ideally, they suggest that you plant three different cultivars for optimal fruit production.
  
  

Grafted Trees

• If space is limited, consider purchasing a grafted cherry tree. A grafted cherry tree will have branches from three or four different cultivars grafted to a root stock (the "trunk" of the tree). The different cultivars function as cross-pollinators, even though they are on a single tree. It is best to have more graftings than you need in the event that one of the graftings is not successful and dies.
  
  

Planting Distance and Pollination

• Cherry trees should be no more than 100 to 200 feet apart to act as cross-pollinators to each other. If cherry trees are not close enough, cut a branch from the cross-pollinating cultivars and place it in a bucket of water underneath the tree you want to produce fruit. Replace the branch daily while the trees are flowering. Cherry trees are best pollinated by bees and other pollinating insects. As a result, avoid spraying insecticides around cherry trees while they are flowering.