Autumn in Hanoi is defined by more than its weather, tree leaves or scenery. It also has a distinctive scent: earthy, pungent and intense, yet strangely evocative when it drifts on the cool breeze. The scent comes from the flowers of the blackboard tree, locally known as hoa sữa (milk flowers), a tropical species that has been part of Hanoi’s landscape since the 19th century.
Recently Hanoi authorities decided to reduce some of these trees following persistent complaints about their fragrance. Why is a scent so closely associated with Hanoi’s autumn being scaled back?
Intense Fragrance As An Autumn Icon
The blackboard tree is native to tropical Asia, including India and much of Southeast Asia, as well as southern China and Australasia.
It is believed to have been introduced to Hanoi in 1889, when the French were shaping the city’s urban landscape. The species was chosen for its large size and broad canopy, which provided shade, as well as its deep roots and ability to withstand strong winds and storms, unlikely to attract harmful insects and well suited to northern Vietnam’s soil and climate. The French planted the first blackboard trees along Quan Thanh Street, spacing them 15–20 metres apart in areas with pavements more than three metres wide and few homes. In subsequent years, the trees were planted along Nguyen Du Street and several other streets.
The trees produce clusters of ivory, creamy yellow or greenish-white flowers from around September to December each year. Their powerful fragrance travels far, carried by volatile organic compounds.
The scent has long divided opinion. Those who dislike it describe it as overpowering, unpleasant and even suffocating, particularly at close range.
At a distance, however, the fragrance becomes softer: a faint, distinctive scent carried on the breeze. Its arrival in autumn, as Hanoi’s weather begins to cool, adds to its appeal. The combination of a gentle chill and the flowers’ lingering fragrance has inspired countless artworks about the city. Many classic songs and poems have been conducted, making blackboard flowers an enduring symbol of Hanoi’s romantic autumn.
For many Hanoians, the scent of blackboard flowers also carries memories of the city. “Even for those who once found the intense fragrance unbearable while living in Hanoi, after leaving, the flowers become a source of nostalgia, unlocking countless memories of the city,” author Le Thi Minh Van wrote on Dan Viet
The Scale Back In 2026
On October 14, Hanoi authorities ordered a review of areas with a high concentration of blackboard trees and called for proposals to relocate some to more suitable locations.
From October 16 to October 20, workers pruned flowering branches from nearly 1,000 blackboard trees along 13 streets. Among the streets proposed for changes is Nguyen Du street, known for its iconic rows of blackboard trees dating back to the 19th century. Under the proposal, the trees would gradually be thinned out and replaced with golden oak, a native species also familiar to Hanoi residents.
The move immediately sparked controversy.
Some residents, particularly those living along streets lined with blackboard trees, support the proposal. They say the dense planting and proximity to their homes make the fragrance overpowering and unpleasant, disrupting their daily lives. Removing or relocating some of the trees would make their surroundings more comfortable. Others who dislike the scent share this view.
Others who cherish Hanoi argue that this distinctive scent is woven into the city’s identity, particularly that of Nguyen Du Street. Cutting down or replacing the trees risks erasing something unique to the city–something that lives on in many people’s memories of Hanoi.
In fact, for years, Hanoi has previously relocated blackboard trees from streets where they were planted too densely. In 2019, trees from several streets were moved to the Nam Son solid waste treatment complex to provide shade and help mask unpleasant odours. In 2023, as part of plans to upgrade Nguyen Chi Thanh Street, authorities proposed relocating around 80 blackboard trees and replacing them with more suitable species. It was never carried out.
Regarding their proposed replacement with other trees, a city representative said any relocation would depend on an assessment of each tree’s condition and its contribution to the streetscape.
Between Urban Memory And Everyday Life
Controversy over the intense scent of blackboard trees has persisted for years. Its resurgence in recent years has been driven not just by the fragrance itself, but also by weather conditions and the density of the trees across Hanoi.
The scent is at its most evocative when it drifts gently through Hanoi’s cool autumn air. In recent years, however, the season has become less reliably cool. Climate change has brought different weather conditions with heat and humidity, turning a fragrance celebrated in poetry into something unbearable.
Hanoi also has a large population of blackboard trees. According to the Hanoi Department of Construction, the city has approximately 14,400 blackboard trees, making them its fourth most commonly planted tree, after sấu (26,400), crape myrtle (17,500) and royal poinciana (16,000). Densely planted and flowering simultaneously, the trees have turned the delicate scent into a source of dread for many residents.
The debate over blackboard flowers, then, goes beyond whether their scent is pleasant. It asks whether a fragrance woven into Hanoi’s identity still has a place in the modern city, and what happens when nostalgia becomes a daily discomfort for those who live there?
While the trees themselves are supported to be planted in the more spacious area, and far away from residents’ home, the decision to remove it totally from Hanoi, would warrant reconsideration.
The scent of blackboard flowers has become part of Hanoi’s collective memory, woven into both poetic recollections and memories of daily discomfort. When autumn arrives and the first cool breeze sweeps through the city, many Hanoians instinctively think of its distinctive fragrance.
As French sociologist Maurice Halbwachs wrote in The Collective Memory: “The place a group occupies is not like a blackboard, where one may write and erase figures at will.”
Moving a tree may change the landscape, but it cannot simply erase the memories attached to it. Tree planting in Hanoi therefore calls for a thoughtful approach. Rather than planting a species widely for its symbolic value or removing it entirely in response to complaints, the histories, memories and living conditions of residents should be taken into account, allowing these experiences to inform the shaping of the urban landscape.
This approach would allow Hanoi to preserve its memories without turning the city into a museum. Reducing the density of blackboard trees is a reasonable step. The next challenge is how to keep their fragrance a defining part of Hanoi, while not eliminating the needs of those who live there.
