The question of whether orchids smell bad has a complicated answer, rooted in the incredible diversity of the Orchidaceae family, which contains tens of thousands of species. Orchid fragrance is not a fixed attribute but a highly variable trait. Some species produce intensely sweet, floral, or fruity aromas, while others intentionally generate smells that humans find strongly offensive, such as decaying matter or mold. This difference in fragrance is entirely dependent on the specific evolutionary strategy of the individual orchid species.
The Biological Role of Orchid Fragrance
The production of scent by an orchid is not for human enjoyment but serves as a precise chemical signal for reproduction. Floral scents are mixtures of volatile organic compounds (VOCs) that function as advertisements to attract specific pollinators from a distance. The chemical profile of a flower’s scent has co-evolved to match the sensory preferences of a single species or type of insect, bird, or bat.
This signaling mechanism is highly specialized, ensuring that the orchid’s pollen, packaged in masses called pollinia, is transferred efficiently. Some orchids provide a direct reward, like nectar, using a sweet fragrance to guide a pollinator to the source. Other species employ an elaborate form of deception, using fragrance to lure a pollinator without offering any food reward.
One sophisticated strategy involves mimicking pheromones, which are chemical compounds used for communication. For example, some Ophrys orchids emit a scent that perfectly imitates the sex pheromones of a female wasp or bee. This powerful lure causes the male insect to attempt to mate with the flower, a process called pseudocopulation, which results in the transfer of pollen. Certain orchids also attract male euglossine bees by producing species-specific scent mixtures, which the bees collect and store to use as cologne for attracting mates.
Decoding the Diversity of Orchid Scents
Orchid scents exist on a continuum from delightful to disgusting. The quality of the fragrance is directly linked to the diet and habits of their target pollinator, explaining why a single family of plants can produce such radically different odors.
The Foul Fragrances
Orchids that smell bad to humans use the offensive odor to attract flies and beetles that feed on decomposing organic matter. The genus Bulbophyllum, one of the largest in the orchid family, contains many species specializing in this type of pollination. These flowers emit volatile compounds that mimic the smell of decay, such as rotting meat or fungi.
The fragrance of Bulbophyllum phalaenopsis has been described as smelling like ripe roadkill, while Bulbophyllum beccarii is known for a powerful odor of decaying animals. These foul-smelling flowers often have dull, reddish-brown coloration and hair-like structures, which enhance the visual illusion of carrion or mold to attract their fly and beetle partners.
The Pleasant Fragrances
In contrast to the carrion flowers, many orchids produce aromas highly prized by humans, often mimicking everyday scents. These pleasant fragrances typically attract pollinators like bees, moths, and butterflies, which are drawn to sweet, floral, or fruity notes. The popular Oncidium Sharry Baby, for example, is known for its strong scent of chocolate or vanilla, a fragrance that attracts certain bees.
Other species offer a variety of gourmand and spicy notes. The small flowers of Maxillaria tenuifolia are famous for their distinct, ripe coconut aroma. Some Cattleya species release sweet, citrus, or spice fragrances. Certain night-blooming varieties, such as Brassavola nodosa, release a powerful lily-of-the-valley or citrus scent in the evening to attract nocturnal moths.
The Scentless Majority
Despite the existence of intensely fragrant species, the majority of the world’s orchids have no noticeable scent at all. Many mass-produced hybrid orchids found in garden centers, particularly those in the Phalaenopsis genus, have been bred for visual traits like long-lasting flowers and striking color. This breeding often occurs at the expense of fragrance. In these cases, the species either relies on visual cues alone or has lost its scent production capability during hybridization.
Environmental Factors Affecting Scent
The strength and presence of an orchid’s fragrance fluctuate dramatically based on several environmental triggers. The time of day is a significant factor, directly linked to the activity period of the target pollinator. Orchids pollinated by daytime insects, such as bees, typically release their scent in the morning, while those pollinated by moths, like some Angraecum species, are powerfully fragrant only at night.
Temperature also plays a substantial role because floral scents are composed of volatile organic compounds (VOCs). Warmer temperatures increase the volatility of these compounds, which generally results in a stronger, more intense fragrance. Conversely, a drop in temperature can significantly reduce the perceived smell.
The amount of light, particularly sunlight, can intensify the fragrance of many day-scented orchids. Plant health is also a factor; an orchid that is stressed, dehydrated, or past its prime blooming period will emit a weaker fragrance or none at all. The scent typically fades as the blooms age, often stopping completely a few days before the flower wilts.