Pollination of Wild Blueberries

Thursday 7 July 2022

Atlantic Canada is known for its delicious, locally grown wild blueberries. However, growing blueberries can be complicated, and relies on pollinating insects such as honey bees. In this blog, we will discuss wild blueberry flowers and how they are pollinated. We will also give a quick update on ATTTA’s wild blueberry research and the next steps in one of our exciting projects. 

Pollination of Wild Blueberries

Each individual wild blueberry plant is called a clone and can grow to around knee height. The leaves are overt and oval-shaped with smooth edges. The flowers grow in clusters and the corolla (petals) take on a bell shape with greenish-white or pinkish coloring. Protected inside the flower are multiple stamens containing anthers that hold pollen (male reproductive cells). At the base of the flower are the ovary and ovules. Extending out of the flower is the style that ends at the stigma. Due to the shape of the flower, wind is not considered a pollinating factor.  This means insects are the only way pollination can occur.

Figure 1: Diagram of cross-section wild blueberry flower in bloom (Image: Drummond, 2019)

Figure 2: Honeybee on wild blueberry flower (ATTTA©2022)

During the wild blueberry bloom in warm months of May and June, the stigma responds to movement created by attracted insects causing the anthers to release pollen. Therefore, when a honey bee or bumble bee visits a flower, released pollen attaches to their body hairs to be transported to subsequent flowers they visit. This transport is essential as it distributes male reproductive cells from one individual blueberry plant to another.  This allows for the reproduction of the plant and the forming of fruit. After an individual flower has reached the end of its blooming period, the petals fall off, leaving the green ovary and ovules. If pollinated adequately, the process of fruit set will begin as the ovary matures into seeded fruit. It starts with bloating of the ovary as a small, round, white-green fruit, ripening to a dusted blue shortly afterwards. 

Figure 3. Fruit set after successful pollination and resulting from the swelling of the ovary, immature fruit is shown as well as one ripe blue berry (ATTTA©2022)

Pollination is key to fruit set on wild blueberries, making it essential to have an abundance of pollinators on blueberry fields. Here in Atlantic Canada, honey bees and bumble bees are commonly tasked with this critical job. Managed honey bee colonies are easily added to fields, bringing an abundance of pollinating capacity. Colonies brought in should be appropriately strong and ideally provide at least one forager bee per square yard (Drummond. 2002). This will, among other factors, help determine the stocking density of honeybee colonies needed for individual fields.  

Honey bees provide adequate numbers to pollinate multiple blueberry flowers and have small bodies that can get inside the bell-shaped flower and shake the pollen loose. Managed or native bumble bees are phenomenal and unique pollinators, as well. Their size and buzzing ability effectively shake out pollen and distribute large quantities from one clone to another. Their extra-long tongues allow them to access and pollinate some of the more closed-off flowers that honey bees may not be able to reach. They are also more resilient to pollinating across a broader range of weather conditions. In spite of being less efficient individually, honey bees have the sheer numbers to pollinate many flowers.

Now that the fruit is beginning to develop on blueberry fields, the Atlantic Tech Transfer Team for Apiculture will be continuing with one of our ongoing pollination projects. In May, we visited wild blueberry fields in NB, NS, and PE to assess honeybee hive strength and percent bloom.  In the upcoming weeks, we will return to these fields and evaluate the number of open blooms which have transformed into fruit.  This determination is called fruit set and is an indication of pollination success. This measure in addition to others, such as number of berries at harvest, fruit weight and seed counts, allows us to evaluate the impact that honey bees have ultimately on the final yield.  Stay tuned for updates on this work as the season progresses! 

Written by Rebecca Campbell, ATTTA Summer Research Assistant rcampbell@perennia.ca

Drummond, F.A. 2019. Over-informed on IPM - Episode 006: Wild Blueberries and Their Wild Pollinators. University of New Hampshire. https://extension.unh.edu/blog/2019/05/over-informed-ipm-episode-006-wild-blueberries-their-wild-pollinators.
Drummond, F.A. 2002. Honeybees and blueberry pollination. University of Maine Coop. Ext. Wild Blueberry Bulletin No. 629.

Connecting with ATTTA Specialists


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