The Bing cherry tree is one of the most widely recognized and sought-after sweet cherry varieties, prized for its large, firm, dark-red fruit. Producing a worthwhile harvest requires specific horticultural planning beyond simply planting a single tree. Growers must strategically choose and plant a second, compatible cherry variety to ensure the Bing tree can successfully produce fruit.
Why Bing Cherry Trees Require Cross-Pollination
Like many sweet cherry varieties, the Bing cherry is self-unfruitful, meaning it cannot set fruit using its own pollen. This is due to a genetic mechanism called gametophytic self-incompatibility (GSI). The tree possesses a pair of specific genes, known as S-alleles, which govern the pollination process.
When a pollen grain lands on the flower’s stigma, the pistil checks the grain’s S-allele against its own two S-alleles. If the pollen’s single S-allele matches either of the tree’s two alleles, the flower chemically rejects the pollen, preventing fertilization.
The Bing variety is classified into Incompatibility Group III, sharing its S-alleles with varieties like Royal Ann and Lambert. Since these varieties share the same genetic markers, they are cross-unfruitful and cannot pollinate each other. Therefore, a successful pollinizer must belong to a different incompatibility group, guaranteeing the pollen carries a non-matching S-allele.
Identifying the Ideal Pollinizer Cultivars
Selecting the correct pollinizer is crucial for a successful Bing cherry harvest. The pollinizer must be a different cultivar, belong to a compatible S-allele group, and have a bloom period that perfectly overlaps with the Bing tree’s mid-season flowering. The partner must be ready to release pollen at the same time the Bing tree flowers.
Excellent cross-compatible varieties include ‘Van’ and ‘Rainier,’ which belong to Incompatibility Groups II and IX, ensuring genetic compatibility with Bing’s Group III status. These varieties have bloom times that align well with Bing, making them reliable choices for commercial and backyard growers. The ‘Black Tartarian’ and ‘Black Republican’ cultivars are also effective pollinizers for the Bing variety.
Certain sweet cherry varieties are self-fertile, possessing a mutated S-allele (often S4′) that allows them to act as universal pollen donors. Cultivars like ‘Stella’ and ‘Lapins’ fall into this category and are highly recommended. They can pollinate the Bing tree while also producing fruit themselves, making them strong and consistent pollinizer options.
Facilitating Successful Pollination
Once genetically compatible trees are planted, the practical logistics of pollen transfer must be managed to ensure fruit set. The synchronization of bloom time between the Bing tree and its pollinizer is a non-negotiable factor; the flowers of both trees must be open simultaneously for cross-pollination to occur.
The physical distance between the trees is also a significant consideration. For effective cross-pollination, the compatible pollinizer tree should be planted within 50 to 100 feet of the Bing tree. This proximity ensures that the insect pollinators can efficiently move the pollen between the two varieties.
Honeybees are the primary and most effective pollinators for sweet cherries. To maximize the chance of a successful fruit set, professional growers often introduce managed honeybee hives into the orchard when the Bing flowers are at about 5% bloom. Placing hives in a warm, sunny location protected from wind will encourage maximum bee foraging activity.
For small-scale growers without a dedicated pollinizer tree, a temporary measure can be employed during the bloom period. Cutting branches of a compatible, blooming pollinizer variety and placing them in a bucket of water within the Bing tree’s canopy can serve as a temporary pollen source. Avoiding the use of insecticides during the bloom period is a fundamental management practice to protect the insects responsible for pollination.