As Hanoi was being developed into the administrative center of Indochina, the French authorities progressively established a system of streets, parks, and green spaces following a Western urban model. Trees were planted along certain routes and around public buildings, providing shade and shaping the city's appearance.

According to writer Nguyen Ngoc Tien, in 1889, the French established a nursery near Bach Thao (Botanical Garden) to import various tree species from Africa, America, and Europe, combining them with native varieties to test their adaptability. After these trees demonstrated deep root systems, resilience to storms, no attraction to harmful insects, and suitability for the northern region's soil and climate, the French gradually planted them on sidewalks. These included trees like xa cu (Burma padauk), sau (dracontomelon), sao den (Hopea odorata), and hoa sua (milk flower).

The milk flower (scientific name Alstonia scholaris), originating from India and Southeast Asia, typically grows 10-50 m tall. Its leaves are 8-25 cm long and 2-5 cm wide, forming a pyramidal canopy that provides ample shade during the scorching northern summers. Its combined fibrous and taproot system anchors the tree firmly, protecting it from strong winds. The small, ivory-white milk flowers grow in clusters and possess a distinct fragrance.

Leveraging these advantages, the French planted the first rows of milk flowers on Quan Thanh street. They were sparsely distributed, with each tree spaced 15-20 m apart, on streets with sidewalks wider than 3 m and fewer residential homes. In subsequent years, milk flowers were planted on Nguyen Du street and a few other locations.

"In the past, most townhouses were low, and the large milk flower trees grew taller than the rooftops, emitting a faint, pleasant scent that was not bothersome", Mr. Tien said.

Milk flowers bloom in autumn. Photo: The Bang

Historian Duong Trung Quoc praised the meticulous selection and distribution of trees by the French, viewing it as a strategic urban planning approach. The trees were intended to provide shade, enhance street aesthetics, and were uniformly planted by species and height along each street to define spaces and create distinct identities.

Today, the Old Quarter (or French Quarter) features roads and streets lined with homogeneous tree species, creating unique characteristics for each area. Examples include sao den on Lo Duc street, milk flowers on Nguyen Du and Quang Trung streets, xa cu on Hoang Dieu street, and sau on Phan Dinh Phung and Le Hong Phong streets.

The development of the urban green space system during the French colonial period laid the foundation for the appearance of many Hanoi streets in later years.

Becoming a romantic symbol of Hanoi's autumn

After 1954, Hanoi entered a new phase of development. The city gradually expanded its area, constructed public facilities, and developed infrastructure to serve its residents. Green spaces continued to play a vital role in organizing living environments. Old streets received tree care and additions, while new residential areas and projects also demanded tree planting for shade and aesthetic improvement.

According to Nguyen Ngoc Tien, during this period, a shortage of tree varieties led to the planting of many species on streets, a practice sometimes called "urban forestry." The milk flower was also propagated extensively. With a less dense population, the sparse milk flowers and their faint fragrance carried on the autumn breeze became a source of inspiration for artists and writers. Classic songs and poems emerged in the following years, solidifying the milk flower's status as an indispensable romantic symbol of Hanoi's autumn.

By the mid-1980s, Hanoi experienced significant changes in its economic life and urban landscape. The population grew, construction boomed, and the need for environmental improvement became pressing. Green spaces became an important component in residential areas and newly built roads. Beyond providing shade, street trees were also recognized as elements that shaped the identity of public spaces.

In this context, urban planners prioritized the milk flower. Professor Doctor Nguyen Lan Hung, General Secretary of the Vietnam Biological Industries Association, explained that the milk flower was widely planted due to its rapid growth, broad canopy, year-round greenery, strong root system, and adaptability to various soil types. Compared to planting sau or xa cu, which take decades to provide shade, milk flowers only require a few years.

Milk flowers bloom profusely on Me Tri street, Tu Liem ward. Photo: The Bang

Relocating and pruning milk flowers

From 1990-2010, the trend of planting milk flowers spread to many new streets in the capital, including Nguyen Chi Thanh, Tran Duy Hung, Le Duc Tho, Ho Tung Mau, and Trung Hoa. Each street saw hundreds of trees planted, spaced 4-6 m apart. In some unique cases, like Me Tri street in Tu Liem ward, both sidewalks and the median strip were lined with milk flowers. A 600 m stretch of Trung Hoa street, for instance, had over 130 milk flower trees, with almost no other species interspersed.

According to statistics from the Department of Construction, the entire city has approximately 14,400 milk flower trees, ranking fourth among the most commonly planted species in the capital, after sau (26,400 trees), bang lang (lagerstroemia) (17,500), and phuong vi (flame tree) (16,000). This dense concentration, combined with the simultaneous blooming of flowers, transformed the "faint fragrance" of the past into an overwhelming scent nuisance for residents. Pollen drifting into homes also affected people's health.

Since 2019, Hanoi has relocated many milk flower trees from several streets to the Nam Son solid waste treatment area to utilize their shade and reduce unpleasant odors. In 2023, as part of the plan to upgrade Nguyen Chi Thanh street, authorities proposed moving approximately 80 milk flower trees to replace them with more suitable species, but this plan was not implemented.

Employees of the Green Park Company prune milk flowers on Dao Tan street on 16/10. Photo: Vo Hai

Three years later, the milk flower once again became a hot topic among residents. Dry weather and increasing air pollution, coupled with the simultaneous profuse blooming of milk flowers, created a strong, suffocating scent that caused discomfort. In some apartment complexes, management even used water hoses to diminish the clusters of milk flowers.

In response to public reaction, Hanoi City requested units to review and plan the relocation of milk flower trees in overly dense areas that affect residents' lives, replacing them with other urban tree species. As an immediate measure, the Green Park Company and local wards and communes proactively pruned the flowers of 992 milk flower trees on 13 routes.

Learning from the experience with milk flowers, Nguyen Lan Hung suggested that Hanoi should refine its urban tree selection process. He advised choosing suitable, easy-to-grow trees with broad canopies and year-round greenery, such as sau, bang lang, bang Dai Loan (Taiwan almond), and xoai (mango). The relocation of milk flowers is a reasonable measure because this species should be planted in spacious areas, with limited planting near residential homes. The transplanted trees could be moved to the Nam Son landfill to provide shade and reduce odors.

Writer Nguyen Ngoc Tien proposed that Hanoi should plan for more green spaces, akin to "urban forests," to regenerate multi-layered ecosystems within the city. This would help filter the air and reduce environmental temperatures, making nature more accessible to urban residents. Currently, the area of green space and street trees in the inner city only reaches 2-3 m2 per person, which is significantly lower than the international standard of 9-12 m2 per person.

Doan Loan