Why Do Bradford Pear Trees Stink?
Bradford pear trees emit a distinctly unpleasant odor, often described as rotting fish or gym socks, primarily due to the chemical compound trimethylamine released during their flowering period. This unattractive scent serves to attract specific pollinators, such as flies and beetles, but is unappealing to most humans.
A Brief History of the Bradford Pear
The Bradford pear ( Pyrus calleryana ‘Bradford’) was initially introduced to the United States from Asia in the early 20th century as a blight-resistant rootstock for edible pear trees. In the 1960s, the Bradford cultivar was released as an ornamental tree, prized for its beautiful spring blossoms, vibrant fall foliage, and rapid growth. It quickly became a popular choice for landscaping and street planting across the country. However, its susceptibility to structural weaknesses and its invasive nature soon became apparent, leading to widespread disillusionment.
The Scent of Success (for Pollinators)
While many flowering trees produce sweet, fragrant scents to attract bees and butterflies, the Bradford pear takes a different approach. It emits a strong, pungent odor that mimics decaying organic matter. This seemingly repulsive scent is actually highly attractive to certain pollinators, particularly flies and beetles, which are drawn to the smell of carrion or dung. These insects then inadvertently transfer pollen from one flower to another, facilitating the tree’s reproduction. The key chemical culprit behind this aroma is trimethylamine, a compound also found in decaying fish and other foul-smelling substances.
The Chemistry Behind the Stink
Trimethylamine is a volatile organic compound (VOC) that is released into the air when the Bradford pear flowers bloom. The amount of trimethylamine produced can vary depending on factors such as temperature, humidity, and the specific cultivar of the tree. Warmer temperatures generally lead to a higher concentration of the compound, resulting in a more intense odor. Other compounds likely contribute to the overall scent profile, but trimethylamine is the main driver of the characteristic “rotten” smell.
Other Problems with Bradford Pears
The offensive odor is just one of several issues associated with Bradford pear trees. Other significant drawbacks include:
- Weak Branch Structure: Bradford pears are notorious for their weak branch structure, making them prone to splitting and breaking, especially during storms.
- Invasive Nature: Bradford pears readily cross-pollinate with other Pyrus calleryana varieties, producing fertile seeds that are spread by birds. This leads to the establishment of wild populations of thorny, invasive pear trees that outcompete native vegetation.
- Short Lifespan: Bradford pears typically have a relatively short lifespan, often only lasting 15-25 years.
- Sharp Thorns: As they revert to their natural state through cross-pollination, the resulting offspring often possess sharp thorns, making them difficult to manage.
Alternatives to Bradford Pears
Fortunately, there are many excellent alternatives to Bradford pear trees that offer similar aesthetic benefits without the negative consequences. Consider these options:
- Serviceberry ( Amelanchier spp.): Provides beautiful spring flowers, edible berries, and attractive fall foliage.
- Dogwood ( Cornus florida): Offers stunning spring blooms and vibrant fall color.
- Redbud ( Cercis canadensis): Produces showy pink flowers in early spring.
- Crabapple ( Malus spp.): Features fragrant blossoms and colorful fruits. When selecting a Crabapple variety, be sure to research disease resistance to ensure it is a healthy and long-lasting choice.
Table: Comparison of Bradford Pear and Alternative Tree Species
| Feature | Bradford Pear (Pyrus calleryana ‘Bradford’) | Serviceberry (Amelanchier spp.) | Dogwood (Cornus florida) | Redbud (Cercis canadensis) |
|---|---|---|---|---|
| Spring Flowers | Abundant, White, Unpleasant Odor | White, Fragrant | White or Pink | Pink |
| Fall Foliage | Reddish-Purple | Red-Orange | Red | Yellow |
| Branch Strength | Weak, Prone to Splitting | Strong | Moderate | Moderate |
| Lifespan | Short (15-25 years) | Moderate (40-60 years) | Moderate (30-50 years) | Moderate (50-70 years) |
| Invasive Potential | High | Low | Low | Low |
FAQs: Decoding the Bradford Pear Problem
Why is the Bradford pear still sold in some places?
Despite its known problems, some nurseries continue to sell Bradford pear trees due to their relatively low cost and rapid growth. There is also residual demand from consumers who are unaware of the tree’s downsides. Educating the public about the invasive nature and other issues associated with Bradford pears is crucial to reducing their prevalence. Some states have banned the sale of Bradford Pears.
Is the smell worse at certain times of the day?
Yes, the intensity of the Bradford pear’s odor can fluctuate throughout the day. Generally, the smell is most pronounced during warmer periods when the concentration of trimethylamine in the air is higher. Morning hours, as temperatures increase, and afternoons, when the sun is strongest, tend to be the smelliest.
Do all Bradford pear trees smell bad?
Yes, all Bradford pear trees emit an unpleasant odor during their flowering period. However, the intensity of the smell can vary slightly depending on the individual tree, its age, and environmental conditions.
Can the smell of a Bradford pear make me sick?
While the odor is unpleasant, it is generally not considered toxic. However, some individuals may experience mild symptoms such as headaches, nausea, or dizziness due to the strong smell, especially if they are sensitive to volatile organic compounds.
What can I do if my neighbor has a Bradford pear tree?
Politely discussing the issue with your neighbor and educating them about the tree’s negative impacts is the best approach. Suggesting alternative, more environmentally friendly tree species can be a constructive way to address the problem.
Are there any Bradford pear trees that don’t stink?
No, all cultivars of Bradford pear trees, including those marketed as “improved” varieties, still produce the characteristic unpleasant odor. The chemical compounds responsible for the smell are inherent to the species.
How can I get rid of a Bradford pear tree on my property?
The most effective way to remove a Bradford pear tree is to cut it down and apply herbicide to the stump to prevent resprouting. Glyphosate-based herbicides are commonly used for this purpose. Hiring a professional arborist is recommended for larger trees or if you are unsure about the removal process.
Is the Bradford pear related to other stinky plants?
Yes, other plants produce trimethylamine or similar compounds that contribute to unpleasant odors. Examples include skunk cabbage (Symplocarpus foetidus) and certain species of carrion flowers. The presence of these chemicals indicates that the plant is adapted to attract specific pollinators through the use of scents reminiscent of decay.
How does the Bradford pear’s invasive nature impact native ecosystems?
The rapid spread of Bradford pears can displace native plant species, reduce biodiversity, and disrupt ecosystem functions. Their dense thickets can block sunlight and outcompete native plants for resources, leading to a decline in the health and resilience of natural habitats.
Are there any benefits to having a Bradford pear tree?
While the downsides of Bradford pear trees far outweigh any potential benefits, they do provide early spring blooms that can be visually appealing. However, there are many other trees that offer similar aesthetic benefits without the negative ecological consequences.
What are the long-term consequences of planting Bradford pear trees?
The continued planting of Bradford pear trees will exacerbate their invasive spread, further harming native ecosystems and reducing biodiversity. Additionally, their structural weaknesses will continue to pose safety hazards and property damage risks. Promoting the use of native and non-invasive tree species is essential for creating sustainable and healthy landscapes.
Why weren’t the negative aspects of Bradford pears discovered earlier?
The initial focus was on creating a blight-resistant and ornamental tree. The invasive potential and structural weaknesses became apparent only after the tree was widely planted and had ample opportunity to cross-pollinate and spread into natural areas. This highlights the importance of thorough long-term testing and risk assessment before introducing new plant species into the environment.