Understanding Plant Phenology to Increase Pollination Efficiency

Thursday 16 May 2024

Wild blueberry producers rely on managed pollinators, such as honey bees, to successfully pollinate their crops. Successful pollination depends on many factors, such as weather conditions, pollinator availability, pollinator health, and proper placement of pollinating units. Many plant phenology stages are dependent upon weather conditions, such as dormancy and flowering, so with more knowledge about these phenology stages we may be able to make early predictions for pollination requirements. Stocking density predictions could potentially be done in the fall of the sprout year and hive placement could be determined long before flowers are opening in the fields in the crop year.

Understanding Plant Phenology to Increase Pollination Efficiency

Wild blueberries are grown on a two-year production cycle. The first year is called a sprout year and the second year is called a crop year (Jenson & Yarborough 2004). The blueberry plants grow vegetatively, meaning only stems and leaves, for most of the sprout year. The highest growing points on the stem have dominance over the lower growing points and the lower buds are dormant which is known as paradormancy (Lang et. al 1987). When day length is shortened in the fall, the tip of the plant dies, known as tip-dieback, and the lower growing points are then released from dormancy to become either floral or leaf buds (Barker & Collins 1963). This may be the earliest point at which the amounts of floral buds can be determined and therefore provide an estimate of how many flowers there will be in the crop year. Since stocking density is determined based on the number of flowers, this could be used as the earliest point to determine stocking density of pollination units.

Wild blueberry floral buds go through a winter dormancy to be able to prevent freezing and drought damage. The winter dormancy happens in two stages, endodormancy and ecodormancy (Lang et. al 1987). Endodormancy requires an accumulation of cold temperatures to satisfy. This is known as the chilling requirement and can be measured by chilling hours, which are an accumulation of temperatures between 0-7C (Fraisse & Whidden 2010). Ecodormancy requires an accumulation of warm temperatures to satisfy, and this can be measured by growing degree days, which are an accumulation of daily mean temperatures (Baskerville & Emin 1969). Once both dormancy stages are satisfied, then the floral buds will open and flower.

Endodormant wild blueberry buds (©John MacDonald 2024)


Wild blueberries are self-incompatible, meaning that they do not self-pollinate and rely on a pollinator to cross pollinate with other plants (Reiger 2006). The flowers are only receptive to pollen for eight to ten days after opening, but fruit set rapidly declines four days after flowers open (Drummond 2019). Native pollinators do provide some of the pollination services needed but blueberry producers rely on managed pollinators, such as honey bees and bumblebees to effectively pollinate their crops (Cutler et. al 2012; Bushmann & Drummond 2015). Placement of pollination units at 10 to 20% of the fields total bloom is optimal for good fruit set, with pollination success quickly declining quickly after 50% (Bennett & Byers 2023). Therefore, creating a bloom prediction model will help improve placement of pollination units, so that growers can use this very valuable but limited resource more efficiently.

Honey bee foraging wild blueberry flowers (©ATTTA 2023)


As the wild blueberry season unfolds, we will be presenting a short series on how a better understanding of plant phenology can allow us to more efficiently apply managed insect pollinators.  Check back in for more information over the next few weeks.

Written by John MacDonald, ATTTA Seasonal Apiculturist



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Connecting with ATTTA Specialists

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