SEOUL: Autumn is in full swing in Seoul, where ginkgo trees are laden with golden foliage, their delicate leaves fluttering to the ground with every gust of wind and carpeting the streets in yellow.
But beneath this picturesque canopy lies a less pleasant reality – a stink that has been likened to dog poop, vomit or sweaty socks.
The foul odour comes from the fleshy outer coat of fallen ginkgo seeds. When crushed, the pulp releases two pungent compounds. One is butyric acid, which is found in vomit and rancid butter, and the other is hexanoic acid, known for its cheesy odour.
This fleshy outer coating surrounds a hard, shell-like layer, beneath which lies the edible ginkgo kernel, which would be more familiar to Singaporeans as one of the key ingredients in the traditional dessert soup cheng tng.
Only female ginkgo trees produce the fleshy, foul-smelling seeds, while male trees produce pollen but do not bear fruit.
In Seoul, where the ginkgo biloba species account for nearly one in three street trees, the pungent smell of its fruit that permeates city sidewalks every autumn season has sparked a different kind of stink this year.
While district authorities have been gradually replacing female trees with male ones in response to residents’ complaints about the stench, the efforts have drawn objections from environmentalists, who argue that removing mature trees to tackle a seasonal nuisance comes at an environmental cost.
In July 2026, the Seoul branch of the Korea Federation for Environmental Movements (KFEM), an environmental non-governmental organisation, released a report estimating that at least 792 ginkgo trees would be removed across Seoul this year as part of tree-replacement projects by district authorities.
“The value of a single mature ginkgo far outweighs a few weeks of bad smell,” said Jo Hae-min, an activist with KFEM.
She warned city officials against giving in to “the complaints of a vocal few”, calling instead for institutional guidelines that assess street-tree management based on data, risk assessments and broader community feedback.
Many of Seoul’s estimated ginkgo street trees were planted from the 1970s onwards, when the city designated the ginkgo as its official tree in 1971 to symbolise the development and prosperity of the nation’s capital.
At that time, it was difficult to distinguish between male and female trees until they reached reproductive maturity, which could be between 15 to 20 years after planting. As a result, saplings were often planted without knowing whether they would eventually bear fruit.
It was only in 2011, when South Korea’s National Institute of Forest Science developed a DNA-based technique to identify male ginkgo trees at the seedling stage, that authorities were able to select male saplings for planting rather than waiting decades for the trees to mature.
Data from the Seoul Metropolitan Government shows that there are nearly 100,000 ginkgo trees planted along its city streets as of end 2025 with the proportion of female ginkgo trees falling by 18.5 per cent in the past four years as district governments gradually replaced female trees with male trees.
Catch, shake and clear
Apart from replacing trees, the authorities are also adopting the less drastic measures of installing funnel-shaped nets on the trees’ lower branches to catch falling fruit, or using mechanical harvesters that shake the fruit off the branches and clearing it from the streets.
Ginkgo trees hold cultural and historical significance on the Korean Peninsula, where they have traditionally been planted at royal academies and Confucian shrines as symbols of learning and moral cultivation, as well as for their remarkable resilience.
Apart from their exceptional longevity, ginkgo trees are prized for their resistance to pests and diseases, as well as their ability to help improve urban air quality by absorbing gaseous pollutants and trapping airborne particles such as fine dust.
South Korean news agency Newsis reported on Oct 21 that the Seoul Metropolitan Government, in response to its queries about the planned replacement of 792 ginkgo trees, said the trees were not being targeted simply because they were female.
Instead, the city said the replacement plans took into account the difficulty of managing fallen fruit in certain locations, such as narrow pavements where there was insufficient space to install collection nets, or busy pedestrian areas such as bus stops and school routes.
Following the backlash, the city said it would substantially scale back the replacement programme for the year, relying instead on fruit collection and nets to manage the problem. Tree replacement would be limited to cases involving safety concerns, such as trees competing with overhead power lines or those classified as high-risk, as well as trees in particularly busy pedestrian areas such as bus stops.
Seoul resident Choi Ji-soo, 45, has mixed feelings towards the ginkgo trees.
She loves their golden colour but prefers to appreciate the beauty from a distance because she dislikes the smell.
“When I step on the fruit, they soil my shoes and make them stinky. The fruit flesh also makes the street slippery and can be a hazard,” she said.
The engineer is supportive of replacing female ginkgo trees with male trees.
“I don’t see it as damaging nature, but more of a way to preserve the ecological benefits of ginkgo trees while effectively solving urban issues like severe odour and slipping hazards at the same time. I think it is a practical and necessary compromise,” said Choi. - The Straits Times/ANN
