Callery pear (Pyrus calleryana) was first introduced to the Pacific Northwest from China in the early 20th century. At that time, a bacterial disease had been infecting pear trees in the many orchards in Oregon and Washington States. Scientists searched the world over for new varieties of the genus Pyrus that might be resistant to the “fire blight” as it was called due to the blackening of the leaves and branches caused by the bacteria. Seeds of the Callery pear were among many of the varieties of pear imported. Scientists with the USDA continued to maintain plants from the original seeds throughout the century.
In the mid-1950’s a scientist named John Creech took notice of a 33-year-old Callery pear grown from the original seeds collected from China. He believed the tree had potential for planting as an ornamental. Callery pear was attractive and tended to be disease free and hardy.
The Callery pear produces a mass of five-petaled white flowers lasting for a few weeks in early spring, before most other trees have broken bud. The leaves are leathery, with a dark-green sheen on the upper surface but with a duller undersurface. They are oval to heart-shaped, about two to four inches long and arranged alternately along the stems. The leaves remain beautiful and unblemished all through the growing season. Then in late fall, the leaves put on another show of fall color from yellow to crimson red.
Creech propagated a multitude of these trees, each one a clone of the original stock. He named his new variety, Bradford pear. He planted two-year old Bradford pears in a test trial in a suburb in Maryland. His trees grew beautifully and became popular before being released as a commercial cultivar in 1961. This tree was rapidly propagated and sold throughout the United States to be planted in yards, boulevards, and commercial properties. The tree was naturally genetically programmed to not self-seed, so there was no concern of this plant escaping from where it was planted. With so many attributes what could go wrong?
Unfortunately, a host of things have gone wrong with the introduction of this non-native tree. For decades, it has aggressively invaded agricultural land, natural areas, wetlands and roadsides, crowding out native species and disrupting entire ecosystems. One of the oversights in planting Callery pear was the fact that if pollen from any other viable Pyrus (pear) tree contacted the flowers of a Bradford pear, the tree could produce seeds. A host of other cultivars of Pyrus were planted into the environment. Bees visiting the flowers of another cultivar carried pollen to Bradford pears and many of them began to produce seeds.
In no time, several species of birds learned to eat the small fruits of Bradford pears and other varieties. The seeds were then dispersed from their droppings across the landscape establishing new plants and new populations of this non-native tree. Ecologists began to take notice of the spread of the Callery pears outside of lawns and city streets by the early 1980’s.
As the Callery pear is rapidly displacing native vegetation, a major concern is that it does not serve as a host plant for most of our native insects. Insects serve as the primary food for birds, adult and young, and for a wide range of mammals, reptiles and amphibians. As Bradford pear takes over a habitat, its dense foliage shades out the understory and seedlings of native shrubs and trees. Deprived native vegetation, the ecosystem will lose its diversity of insects and the natural food web disintegrates.
Currently, the Bradford pear and other cultivars of Callery pear are still available in nurseries and places like Lowe’s and Home Depot. Efforts are being made to ban the sale of all varieties of Callery pear. Ohio and South Carolina already have scheduled bans on the sale and distribution of these plants.
The refuge has had some infestations. The following quote is from Victor Elam, refuge manager. “Bradford/Callery pear trees have been found on the refuge on our mainland properties near the office and on Middle Island. Although it is not documented elsewhere, we cannot preclude its presence anywhere on the refuge. The refuge waged war on these highly invasive trees in the past year and have found that with good effort, we can keep them in check, where we have found and treated them.”
Many scientists and the USDA recommend that we remove these trees from our landscapes. It is imperative that we stop planting them anywhere. Good alternatives include service berry, winter berry, hawthorn or even crab apple. Contact your local County Extension agent for more advice on how to remove these trees.