Most fruit trees need cross-pollination to produce fruits. Most sweet cherries are self-unfruitful and require cross pollination with another variety as the pollen source. Cross-pollination is when the transfer of pollen occurs between two varieties.
For a sweet cherry tree to produce fruit, pollen must travel from the male part of the flower, the stamen, to the female part of the flower, the pistil. The anther which is located in the stamen produces the pollen. Then, when the pollen lands on the stigma to begin formation of the pollen tube. Although cherry flowers have both male and female structures, they are unable to fertilize themselves. Cherry trees require a secondary pollen source and an insect to move the pollen to another cherry tree. Pollinating insects help by moving the pollen from one flower part to the other. Probably the most important pollinating insect is the honeybee. Sweet cherry trees require pollen from a different cherry tree nearby to make fruit. These are known as pollinizers. Both insects and other cherry varieties are considered pollinators of cherries.
Pollen moves from tree to tree with the assistance of helpers such as water, wind, insects, birds and some mammals. The highly concentrated, sugary nectar of sweet cherry blossoms attracts honeybees, as does the protein-rich pollen. For each trip a bee makes to an area with cherry trees, it can visit more than 400 flowers. Once honeybees find a good food source, they will then return repeatedly, making them an important cherry pollinator.
Sweet cherry trees are only compatible with other sweet cherry trees. They need to blossom at the same time of the season, which is usually mid to late in the season for sweet cherries. There can be problems even if the trees are compatible with each other however. Lack of rain, high winds or frost can damage buds before they blossom. Fruit trees form their flower buds in the fall. Excessive winter cold or even a late-spring frost can kill buds and blossoms.
Derek Kramer, Hayden Shapiro, Jeremy Blanchard, Maddy McKay, Ingrid Jimenez