Many people encounter the perplexing experience of a beautiful blooming tree that emits an unpleasant odor. This phenomenon often prompts questions about the specific species and the reasons for their foul-smelling flowers. While these trees boast attractive blossoms, their scents can range from fishy to rancid, affecting springtime enjoyment.
Common Odorous Trees
Several tree species are known for their malodorous blooms. The Callery Pear (Pyrus calleryana), especially the ‘Bradford’ cultivar, is a common source. Widely planted for its early spring white flowers and rapid growth, its blossoms release a pungent, fishy odor. Introduced from Asia in the early 1900s, this tree was popular for urban landscaping but is now an invasive species in many states.
The female Ginkgo Biloba tree is another source of unpleasant odors. While its fan-shaped leaves are admired, only female trees produce fruit. When ripe and crushed, this fruit emits a strong smell akin to rancid butter, vomit, or old cheese, due to a chemical compound within it. The Tree of Heaven (Ailanthus altissima), an invasive species from China, also releases an offensive smell from its flowers and bruised leaves, often compared to rancid peanuts or burnt cashews.
Why These Trees Smell
The unpleasant odors produced by these trees serve an evolutionary purpose: attracting specific pollinators. Unlike sweet-smelling flowers that appeal to bees or butterflies, foul-smelling blooms target insects like flies and beetles. These insects are drawn to decaying organic matter, and the trees mimic these scents to lure them.
The Callery Pear’s fishy smell comes from compounds like trimethylamine and dimethylamine. The female Ginkgo’s fruit contains butyric acid, the chemical found in rancid butter, which attracts carnivores for seed dispersal. Recent research indicates that some foul-smelling flowers have evolved genetic pathways to produce strong chemicals, such as dimethyl disulfide, which smells like rotting flesh. This biological strategy aids reproduction.
Dealing with Unpleasant Tree Odors
Managing odors from existing trees depends on the species and issue severity. For female Ginkgo trees, the smell primarily comes from fallen, rotting fruit. Regularly collecting the fruit can significantly reduce the odor. While some chemical sprays exist to prevent fruiting, their effectiveness varies and they are difficult for homeowners to apply.
Callery Pears pose a problem beyond their smell; they are highly invasive and outcompete native plants. Removal is often recommended, especially for mature, fruit-bearing trees, to prevent further spread. Control methods include manual removal of small saplings or chemical treatments like foliar herbicides, basal bark applications, or cut-stump treatments for larger trees. Removing all root fragments is important to prevent regrowth, as Callery Pears are vigorous resprouters. Professional consultation is advised for tree removal, particularly for larger specimens or invasive species.
Planting Pleasant Alternatives
When selecting trees for landscaping, choosing species with pleasant or neutral odors can prevent future issues. Many desirable native trees offer aesthetic appeal without foul smells. Flowering dogwoods (Cornus florida), for example, provide showy white or pink flowers in spring and attractive fall foliage. Serviceberry (Amelanchier spp.) is another excellent choice, offering delicate white flowers in spring and edible fruits.
Sweetbay Magnolias (Magnolia virginiana) are known for their sweet, lemony white blooms, appearing sporadically over several weeks. Crabapple trees (Malus spp.) produce a flush of sweet-smelling blooms in various sizes and colors, with fruitless cultivars available to avoid mess. Other alternatives include redbuds (Cercis canadensis) with their distinctive purple-pink flowers and certain cherry tree varieties with subtle, sweet almond scents.