Cherry fruit production relies entirely on the successful transfer of pollen between blossoms, a biological process known as pollination. For a cherry tree to set fruit, pollen from the anther of one flower must reach the stigma of another, leading to fertilization. Cultivating a fruitful cherry harvest depends on ensuring this transfer occurs effectively and reliably. A major factor in maximizing the potential yield requires determining the appropriate proximity to a compatible partner.
Understanding Cherry Pollination Needs
The requirement for close proximity is determined by the specific cherry variety being grown. Cherries fall into two main categories based on their reproductive needs: self-fertile and self-unfruitful. Self-fertile varieties, which include most sour or tart cherries, possess the ability to produce fruit using only their own pollen. These trees can be planted alone and still yield a crop, though production may increase with a nearby partner.
Most sweet cherry varieties, such as ‘Bing’ or ‘Rainier’, are considered self-unfruitful and must engage in cross-pollination to set fruit. This involves transferring pollen from a genetically distinct and compatible partner tree. If a self-unfruitful tree receives pollen from another tree of the exact same cultivar, it will not produce fruit. The two compatible varieties must also bloom simultaneously for the transfer to be successful.
Determining the Optimal Distance
The physical distance required between cherry trees for effective cross-pollination is dictated by the working range of the primary pollinating agents. For a reliable transfer of compatible pollen, the optimal distance between a self-unfruitful cherry tree and its pollinator partner is generally considered to be 50 to 100 feet. This range ensures the foraging insects can move efficiently between the two trees during the short blooming period.
While the primary pollinators can travel much farther, their effective working radius is significantly shorter for consistent fruit set. If compatible trees are spaced more than 100 feet apart, the reliability of cross-pollination decreases noticeably. Beyond 200 feet, the chances of reliable pollen transfer become low, particularly in backyard settings with fewer concentrated pollinators.
In commercial orchards where trees are planted densely, the spacing between trees is much smaller, sometimes 5 to 30 feet apart, depending on the rootstock. These closer plantings maximize the chances of a pollinator moving from one variety to the next. For backyard growers, placing compatible partners within the 50 to 100-foot radius is the most practical way to encourage the necessary pollen exchange.
The Role of Insect Pollinators
Cherry trees are almost exclusively pollinated by insects, not by wind, necessitating close proximity. Honeybees are the most commonly managed insect used for this purpose, but native bees like mason bees and bumblebees also play a significant role. These insects carry the sticky, heavy cherry pollen from one flower to the next on their bodies.
A key aspect of bee behavior is ‘flower fidelity,’ meaning a bee tends to visit the same type of flower repeatedly during a single foraging trip. This behavior is beneficial in an orchard, as it ensures the pollen collected from the pollinator tree is deposited onto the main cultivar. The effective distance of this transfer is reduced under unfavorable weather conditions.
Bee flight activity is heavily influenced by temperature, decreasing dramatically below 55°F (13°C) and ceasing altogether in heavy rain or high winds. Since cherries bloom early in the spring when weather is often cool or wet, the bees’ ability to travel long distances is hampered. Placing the compatible partners close together mitigates the risk of poor weather limiting the required pollen transfer.
Solutions for Limited Space and Incompatible Trees
When planting a second compatible tree is not possible due to limited space or when an existing tree is incompatible, alternative methods can be used to achieve cross-pollination. One effective temporary solution involves using a “pollen bouquet.” This technique requires cutting flowering branches from a compatible cherry variety and placing them in a container of water near the tree that needs pollination.
The pollen from these cut branches remains viable for several days, allowing foraging bees to visit the bouquet and then carry the compatible pollen to the flowers on the main tree. This method artificially introduces the necessary pollen source within the bee’s immediate working radius.
A permanent solution for space constraints is to graft a compatible scion, or small piece of branch, onto the existing cherry tree. This results in a single tree that bears two compatible varieties, guaranteeing the pollen source is always immediately available for the insects. Furthermore, selecting a genetically self-fertile sweet cherry variety, such as ‘Stella’ or ‘Lapins,’ eliminates the need for any second tree entirely, making it an excellent choice for small gardens.