Any experienced blueberry grower will tell you that the key to producing a good crop is pollination. Understanding the basics of blueberry bush pollination and how it occurs can help growers select the right cultivars and increase their yields.
Insects and Pollination
Insects don't visit flowers for pollen but for nectar. When they enter the flower, pollen is released through a pair of pores at the tip of each anther. The insect then carries the pollen to the next flower it visits. When the insect brushes against the stigma of the next flower, the pollen is removed and pollination occurs. Because blueberry pollen is heavy and sticky, it cannot be carried by the wind like other pollens. It must be transported by insects.
Importance of Bees
Bees are almost essential to the pollination of blueberry bushes. Bees tend to remove more pollen from blueberries because they vibrate the flower during their visit, called "sonication." However, some bees remove nectar by drilling holes into the flowers. Because they do not go into the flower, they are ineffective pollinators.
Self- vs Cross-Pollination
Depending on the type, blueberries may or may not require cross-pollination. Cross-pollination means that more than one cultivar of blueberry is required for the bush to produce berries. Most rabbiteye, lowbush and half-high blueberries require cross pollination. They are often described as self-unfruitful, self-incompatible, or not self-fertile. Northern and southern highbush blueberry bushes do not and may be described as self-fertile, self-compatible or self-fruitful.
Cross-Pollination and Production
Although highbush blueberries do not require cross-pollination, studies show that it will increase yields and produce larger berries. According to a University of Georgia study, blueberry production doubled on bushes that were cross-pollinated as opposed to those that were not.
It is fairly easy to choose cultivars for cross-pollination. First, you must have two bushes of the same type (rabbiteye, lowbush, etc.). Then, select two varieties that bloom at the same time. This will give the greatest window of opportunity for the bushes to be pollinated by insects. The two cultivars should be planted next to each other or in alternating rows. For example, choosing "Duke" and "Bluetta" is a good choice because both are early season blueberries. However, choosing "Duke" and "Elliott," a late-season berry, is not.