The Callery pear, Pyrus calleryana, is a species native to East Asia that has become notorious across the United States. Its most famous cultivar, the ‘Bradford’ pear, was introduced in the 1960s and quickly became a favorite for landscapers and homeowners. This popularity stemmed from its fast growth rate, uniform shape, and the spectacular display of white flowers that arrive early in the spring. The tree was also prized for its tolerance to various soil types and urban pollution, making it ideal for street plantings, but this once-celebrated ornamental has become a serious problem, leading to bans and active removal efforts in numerous states due to multiple severe liabilities.
Structural Weakness and Catastrophic Failure
The most immediate problem for property owners is the tree’s inherent structural weakness, which makes it dangerous and short-lived. This flaw is rooted in the way the branches attach to the trunk, forming narrow, upright V-shaped crotches. These angles lead to “included bark,” where the bark is trapped between the trunk and the branch, preventing a strong wood connection, unlike strong trees which develop U-shaped attachments. The weak V-shaped unions are incapable of supporting the increasing weight of the mature canopy, making the trees extremely susceptible to catastrophic failure under moderate loads, such as heavy snow, ice, or high winds. This splitting often occurs suddenly after only 15 to 25 years of growth, creating significant cleanup and property damage risks, compounded by the fast-growing wood which contributes to a weaker cellular structure.
Aggressive Invasive Spread and Ecological Harm
The Callery pear is now widely recognized as a highly successful invasive species, disrupting natural ecosystems across the eastern and midwestern United States. While the original ‘Bradford’ cultivar was thought to be sterile, the introduction of other Pyrus calleryana cultivars allowed for cross-pollination, leading to the production of viable fruit and fertile seeds readily dispersed by birds and other wildlife. Seedlings quickly establish themselves and grow rapidly, often leafing out earlier than native plants, which shades out and outcompetes native flora for light, water, and nutrients. The pear forms dense, homogeneous stands that displace native species essential for local wildlife, and research indicates that native insects are less likely to feed on the Callery pear, limiting a crucial food source for birds. Due to this invasive nature, the tree has been listed as a noxious weed or invasive species in many states, with some jurisdictions actively banning its sale and cultivation.
Practical Nuisances: Odor and Thicket Formation
Callery pears also present two significant management and sensory nuisances. The flowers, which appear in profuse white clusters early in the spring, emit a notorious and unpleasant odor. This smell is often described as resembling rotting fish, chlorine, or even semen, which can be offensive to people living near the trees.
The second nuisance arises when escaped seedlings revert to a wild, thorny form of the species. When Callery pears hybridize and spread, the resulting offspring develop aggressive, sharp woody thorns that grow into dense, impenetrable thickets. This thorny growth creates obstacles for land management, blocks wildlife corridors, and can damage equipment. Attempting to simply cut down an established tree often results in vigorous resprouting from the stump, encouraging the thorny, invasive form and requiring specialized herbicide treatments for complete removal.