To set fruit, blueberries need to be pollinated with care. I know many gardeners who has flowers but no berries because they think that any old bee will do. Wrong.
Because of the shape of the flower’s anther, the tightly packed pollen remains stuck until some kind of vibration opens the flower, setting it free. It can’t be wind; there is no vibration from a gentle breeze. Just barely enough pollen move to count. Enter the bumblebee. With its sonication, these bees is able to create a cloud of pollen by vibrating muscles of their flight at approximately four hundred hertz. That vibration shakes pollen loose.
How to Get Blueberries to Grow Fruit
Honeybees never do this: They fly right by, land briefly to sip nectar, and depart without dislodging a single grain. So if all you ever see visiting your plants are honeybees, you’ll see something happening but you won’t get much fruit.
Successful pollination relies on the choice of varieties. By all accounts, planting two compatible varieties will significantly increase your yield. Self-pollinated berries tend to be smaller and mealy compared to cross-pollinated berries that gets bigger and firmer. Why? Increased genetic diversity triggers more seed development, which increases auxins in the fruit and helps it grow. Without a partner, rabbiteye is virtualy sterile. Even highbush benefit from proper pairing.
You’ll want to choose varieties whose bloom period overlaps. It is no good if one blooms early and other blooms late, because they won’t share a reproductive window.
Pollen is viable only under certain weather conditions and the bees will be out there foraging accordingly. Below about 50 degrees F, most forage cease. Bumblebees are somewhat hardier (they produce some body heat) than other bee, though even they are slowed down by a chill day. Rain sends flowers closing up shop to shelter their reproductive bits. Wet weather fast-cooks pollen into gooey globs that is no longer viable. A couple of rainy days at prime bloom time can wash off pollen, keep bees indoors and lower the yield potential. For this reason it makes sense to site plants to avoid low spots where cold air collects, or sites where constant wind would limit successful pollination.
Home garden plants support pollinators by providing habitat diversity. Commercial growers use managed bumblebee colonies, but that’s not what’s needed at home, where the goal is to promote native species. Mining bees are active early on cool spring days; mason bees are also effective. Don’t disturb areas of bare soil, that’s ideal nesting habitat for ground-nesting miners. Make sure they have a place to nest too: Offer some bee hotels or provide some hollow stems. Provide food (pollen-rich flowers) for the bees before and after blueberries bloom with some companion flowers such as borage or clover. It’s building an ecosystem instead of simply growing a crop.
Blueberries require proper ecological management in order for them to be successful. That means creating an environment that allow certain pollinators to do their job. You must provide nesting sites for the bees, match bloom times between varieties and maintain correct soil pH. When all of these environmental (and mechanical) factors come together, it’s time for some fruit.