The Callery pear, more popularly known by its cultivar name Bradford, is a beautiful tree initially brought to the United States from Asia in the early 1900s to breed with common pear trees to build up their resistance to fire blight.
They are small to medium-sized trees with teardrop-shaped leaves and finely toothed edges. In the spring, bundles of tiny white flowers sprout – which helps identify the Callery pear tree due to the flower’s foul odor. In the fall, clusters of hard fruits appear, often a delicacy for wildlife throughout the winter.
Callery pear trees are incredibly tolerant of environmental stressors and grow rapidly. Because of such characteristics, around the 1960s, their role expanded beyond simply breeding with other pear trees for pest and disease resistance to becoming a popular ornamental commonly found in parks, landscapes, and communities across the United States.
For decades, the Callery pear tree was the perfect horticultural specimen. But as the trees became overplanted, problems began to emerge, which were unexpected and detrimental to the surrounding landscapes they inhabited.
The Callery pear tree is now considered an invasive species.
The Morton Arboretum states, “Invasive plants have a tendency to spread and disrupt ecosystems in natural areas such as state and national parks and forest preserves. They can out-compete native plants, upsetting the balance of the ecosystem. They can make the habitat less suitable for native plants and animals. Invasive plant species are a significant and ongoing land management concern.”
But just how are Callery pear trees invasive?
Callery pear trees, due to their rapid growth, form dense groupings of trees which dominate the area and rob native plants of the light, nutrients, and water necessary for their survival. Because of their high tolerance to environmental stressors, they can quickly weed out more vulnerable plants that are weakened by disease and insect infestations or unable to withstand long periods of drought, which are common across much of the United States.
Additionally, the early Callery pear trees could not produce fruit because they needed to be genetically different from each other. Over time, the tree naturally evolved into a genetically unique specimen, which bore fruit many people had never seen on the trees before. Because of the influx of fruit eaten and digested by birds and other wildlife, seeds could be spread easily up to great distances, which enabled the trees to proliferate areas they once were absent from.
With the invasive tendencies now apparent, the State of Ohio has become the first state to ban the sale of Callery pear trees, with others expected to follow (South Carolina’s ban goes into effect in 2024). Tree farms and nurseries have already stopped production and availability to customers in Ohio in the hopes of reversing the hold this once popular ornamental tree now has on landscapes and in forests across the country.