The Nanking Cherry (Prunus tomentosa) is a vigorous, adaptable shrub prized for its exceptional cold tolerance. Native to northern China, this deciduous species produces a profusion of delicate, fragrant white or pink flowers very early in the spring, often before its leaves emerge. Following the bloom, the shrub develops small, tart, bright red fruits suitable for fresh eating or processing into jams and jellies. Clarifying the mechanisms required for fruit set is the first step toward successful cultivation of this popular backyard edible.
The Requirement for Cross-Pollination
The Nanking Cherry is generally considered self-incompatible, meaning an individual shrub cannot successfully pollinate itself to produce fruit. This trait requires the transfer of pollen between two separate, genetically distinct plants to trigger fertilization and fruit development. A single Nanking Cherry planted alone will typically flower profusely but fail to set a substantial crop because its own pollen is rejected. For reliable and abundant yields, gardeners must ensure they are planting more than one shrub.
The need for cross-pollination requires more than just planting two bushes of the same named cultivar or from the same batch of cuttings. Plants propagated vegetatively, such as through cuttings, are genetic clones and cannot pollinate one another. The plant’s internal mechanisms recognize the pollen as genetically identical, preventing successful fertilization. To overcome this self-sterility, at least two separate genetic individuals must be present in the planting area.
Selecting and Placing Pollination Partners
To satisfy the requirement for cross-pollination, the most reliable approach is to plant at least two shrubs sourced from different seed batches or distinct cultivars. Since Nanking Cherries are often grown from seed, even un-named plants purchased from different nurseries may offer the necessary genetic diversity. Planting multiple shrubs also increases the likelihood of a heavier fruit set, as more pollen is available for transfer.
Once genetically distinct partners are selected, their placement is important for maximizing successful pollen transfer. Shrubs should be planted relatively close to each other to facilitate insect pollinators. For effective cross-pollination, the plants should be situated within 100 feet of each other, though closer proximity is preferable. Bees are the primary vectors responsible for moving pollen from the flowers of one shrub to the receptive stigma of the other.
The simultaneous blooming of both partner shrubs is necessary for fruit production. The plants must be in flower at the same time for the bees to carry viable pollen between them. Planting partners side-by-side ensures that pollinator insects can easily travel the short distance required to deposit the foreign pollen, securing a harvest.
Non-Pollination Factors Affecting Fruit Production
Even when two genetically distinct Nanking Cherries are planted correctly, environmental or cultural issues can still prevent fruit formation. One common issue is late spring frost, which can damage the delicate flowers that emerge very early in the season. Although Nanking Cherry flowers are resilient to cold, an unexpected hard freeze after the buds have opened can still kill the reproductive parts of the bloom. This damage stops the fertilization process, resulting in no fruit for the season.
Site selection and maintenance are factors separate from the pollination requirement. Nanking Cherries require a minimum of six to eight hours of direct sunlight daily for optimal flowering and fruit set. Poor drainage is detrimental, as the shrubs prefer loamy, well-drained soil and will not thrive in standing water. Excessive nitrogen fertilization, especially from surrounding lawn care, can promote lush foliage growth at the expense of flower and fruit production. When troubleshooting a lack of fruit, first confirm the presence of a compatible partner and then evaluate these environmental conditions.