The Bosc pear is recognizable by its elongated neck and distinctive cinnamon-brown russeted skin. Praised for its complex, sweet-spicy flavor and dense, firm flesh, it holds its shape well when baked, poached, or roasted. Achieving a successful harvest requires a deliberate approach, as the Bosc pear demands a specific partnership with another variety to produce a reliable crop.
Why Bosc Pears Require Cross Pollination
The Bosc pear is highly self-incompatible and cannot effectively pollinate itself. A significant number of pear varieties, including Bosc, produce pollen that is non-viable or sterile, meaning the pollen grains are incapable of fertilizing the ovules in their own flowers. This reproductive barrier is often a result of having three sets of chromosomes, a condition known as triploidy. This genetic makeup prevents the Bosc tree from producing enough effective pollen to set fruit, necessitating the introduction of a compatible pollen source from a different cultivar. Even when cross-pollination does occur, the Bosc tree serves as a poor pollen donor for other varieties because its own pollen is largely ineffective. For a fruit to develop fully, viable pollen must land on the stigma of the Bosc flower and successfully fertilize the ovule. Without this cross-pollination step, the Bosc tree will fail to produce a meaningful crop.
Selecting Effective Pollinator Varieties
Successful Bosc pollination hinges on planting a compatible pear variety that produces viable, fertile pollen. The chosen partner must be a diploid variety, allowing it to generate the robust pollen that Bosc flowers require. The most crucial factor in this selection is the synchronization of the bloom period, as the pollinator’s flowers must be open and shedding pollen concurrently with the Bosc tree’s receptive blossoms. Reliable and widely recommended diploid pollinators for Bosc include ‘Bartlett’ (also known as ‘Williams’), ‘Anjou’, ‘Comice’, and ‘Seckel’. A pollinator tree should be planted within about 100 feet of the Bosc tree to ensure insects can easily carry the pollen between the two varieties. Avoid varieties that are also triploid or have bloom periods that do not overlap with Bosc, as they will not fulfill the necessary pollination role.
Maximizing Pollination Success
Once the correct pollinator variety is selected and planted, the next step is ensuring the pollen is effectively transferred to the Bosc flowers. Pears rely entirely on insects, primarily honeybees, to move the pollen between trees, as they are not wind-pollinated. Pear blossoms are comparatively less attractive to bees than other fruit trees because their nectar has a low sugar content. To compensate, growers often need to place two to five honeybee colonies per acre in an orchard to ensure sufficient activity. Weather conditions are also a major factor, as honeybees reduce or cease foraging activity below 55°F or during periods of high wind and heavy rain. Placing the pollinator trees and the bee colonies in sunny, wind-protected areas encourages maximum bee flight during the brief window of bloom. Furthermore, applying pesticides must be avoided during the flowering period to protect the foraging insects and secure the fruit set.