The Bradford Pear tree (Pyrus calleryana) is widely planted across the United States as an ornamental species, celebrated for its dense, early spring display of white flowers. It was originally thought to be sterile, which contributed to its popularity as a tidy landscape tree. However, the answer to whether a Bradford Pear tree produces fruit is yes. This fruit production, often unexpected by homeowners, is responsible for the tree’s classification as an invasive species.
The Appearance of Bradford Pear Fruit
The fruit of the Bradford Pear (and the Callery Pear species) is not the large, edible pear people typically envision. Instead, they are small, hard pomes. These fruits are generally round and measure less than one-half inch (about 12 mm) in diameter, making them inconspicuous among the tree’s foliage.
The color changes as the fruit matures, starting as yellowish-green before developing into an olive-brown or tan hue, often speckled with pale dots. The interior contains a fleshy pulp that typically holds two to four small, black seeds. The fruit is unpalatable and bitter to humans. It remains hard on the tree until the first hard frost, which causes it to soften and darken, making it more attractive and accessible to wildlife for seed dispersal.
The Requirement for Cross-Pollination
The ability of a Bradford Pear to produce fruit depends on self-incompatibility. The original ‘Bradford’ cultivar was believed to be sterile because it cannot successfully pollinate itself; its own pollen is incompatible with its own flowers. Therefore, a single, isolated Bradford Pear tree will not set viable fruit.
However, the widespread planting of other cultivars of the same species, such as ‘Chanticleer,’ ‘Cleveland Select,’ and ‘Autumn Blaze,’ introduced the necessary genetic diversity. When pollen from a distinct Pyrus calleryana cultivar or a wild Callery Pear tree is transferred, cross-pollination occurs, triggering fruit production. This genetic exchange allows the previously “sterile” ornamental tree to produce abundant, fertile seeds.
Bees and other insects are the primary vectors carrying pollen between these varieties, often over considerable distances. Furthermore, Callery Pear seedlings are often used as rootstock for grafting ornamental varieties. If the graft fails, the vigorous, fertile rootstock can sprout and serve as an additional pollen source, enabling viable fruit formation. This unintended cross-pollination among numerous cultivars causes the massive fruit set now common in the species.
How the Fruit Contributes to Invasive Spread
The abundant fruit of the Bradford Pear drives the tree’s classification as an invasive species across many regions. Once the fruit softens following a freeze, it becomes a food source readily consumed by various animals, including birds and small mammals. These animals digest the fruit’s flesh but pass the small, hard seeds, effectively dispersing them far from the parent tree in their droppings.
The seeds are highly viable and germinate quickly in new locations, leading to the rapid proliferation of wild Callery Pear seedlings. These wild offspring often revert to the species’ original form, characterized by dense, thorny thickets that are difficult to manage. These thickets aggressively invade open spaces, old fields, and forest edges, outcompeting native vegetation, such as dogwoods and redbuds, for light and resources. The resulting monocultures reduce ecosystem biodiversity, posing a threat to native plant and wildlife communities.