The foul odor emanating from certain flowering pear trees is a common and unpleasant experience in many urban and suburban environments. This distinctive smell, often described as a mix of rotting fish or decaying matter, appears suddenly in early spring with the bloom of white flowers. The intensity of the scent can be surprising, considering the tree’s otherwise ornamental appeal. This widespread issue is particularly notable in managed landscapes and along city streets where these trees were once heavily planted.
The Chemical Source of the Odor
The intense, unpleasant smell is directly linked to specific chemical compounds released by the flowers. The primary culprits are volatile organic compounds known as amines, which contain nitrogen atoms. Specifically, two amines, trimethylamine and dimethylamine, are heavily implicated in creating the fishy and putrid scent. Trimethylamine is a compound naturally found in decaying fish and other decomposing organic materials, explaining the common description of the pear tree’s odor.
The flowers release these volatile amines into the air, where they are easily detected by the human olfactory system. Higher temperatures and humidity levels can accelerate the decomposition of the delicate flower tissue, causing a more rapid release of these compounds and intensifying the smell. While some studies suggest other nitrogenous amines like 1-pyrroline may also contribute to the odor, the general consensus points to trimethylamine as the most significant factor.
The Tree’s Pollination Strategy
The biological purpose behind the foul smell is a deliberate evolutionary strategy to ensure successful reproduction. Most flowering plants rely on sweet scents to attract traditional pollinators like bees and butterflies. However, the pear tree’s putrid scent is not meant for these insects. Instead, the smell is an attractant for non-traditional, less-glamorous pollinators.
The decaying-matter aroma is highly appealing to insects that feed on carrion or decaying organic material, such as various species of flies and carrion beetles. These insects, which are active early in the season, are drawn to the odor and inadvertently carry pollen from one tree to another. By attracting a different class of pollinators, the tree secures its reproductive success during a period when traditional pollinators may be less abundant.
Which Pear Trees Are the Main Offenders
The trees primarily responsible for the offensive smell belong to the species Pyrus calleryana, commonly known as the Callery pear. The most notorious cultivar of this species is the ‘Bradford’ pear, which was once widely planted for its uniform shape and showy spring blossoms. Other Callery pear cultivars, such as ‘Aristocrat’ and ‘Redspire,’ also produce the same distinctive, strong odor during their brief flowering period in the early spring.
The smell is characteristic of the ornamental Callery pear and its cultivars, not the pear trees grown for edible fruit. The common edible European pear (Pyrus communis), which produces fruit like Bartlett and Anjou pears, does not emit this unpleasant scent.
The Callery pear was originally introduced to the United States from Asia in the early 1900s for use as a rootstock for edible pears. It later became a popular street tree due to its hardiness and fast growth. Unfortunately, the ‘Bradford’ pear and its related cultivars have since become highly invasive, cross-pollinating to produce fertile, thorny offspring that crowd out native vegetation.
Homeowner Options and Alternatives
For homeowners dealing with an existing Callery pear, the primary management strategy is simply waiting for the brief two-week flowering period to end. Because the tree is considered an invasive species in many regions, arborists now recommend removing them entirely to prevent their spread into natural areas. Removing Callery pears also eliminates the risk of their characteristically weak branch structure failing in storms.
When seeking a replacement, many excellent, native alternatives offer similar ornamental appeal without the ecological or olfactory drawbacks. These alternatives provide multi-season interest and support native insect and bird populations, making them a better choice for the landscape.
- Serviceberry (Amelanchier species) provides delicate white spring flowers, attractive berries for birds, and brilliant fall foliage.
- Eastern Redbuds (Cercis canadensis) produce striking pink or purple blossoms before their leaves emerge.
- Flowering Dogwoods (Cornus florida) offer beautiful white or pink late-spring flowers.