Experts say that to save fallen precious trees, especially old trees, it is necessary to cut off branches and canopy, then rebuild and widen the area of the pot so that the tree has space to develop its root system.
Typhoon Yagi swept through Hanoi, causing about 17,000 trees to fall, including about 2,000 urban trees. In a document on overcoming the consequences of Typhoon Yagi on the afternoon of September 8, Hanoi Chairman Tran Sy Thanh requested relevant units to mobilize all human resources and equipment to clear fallen trees to ensure traffic safety. Trees that need to be preserved, rare and valuable trees, and small trees with a diameter of less than 25 cm that have fallen will be assessed for replanting on site or taken to nurseries for care.
Dr. Trieu Van Hung, forestry expert and former Chairman of the Vietnam Forestry Science and Technology Association, said that to ensure that fallen trees survive and grow, branches and canopy must be cut. Before replanting, the area of the pot must be widened to give the tree space to develop its root system.
Newly replaced trees, or trees that are currently being wrapped in sacks or plastic, need to be removed. “If left unwrapped, the roots will have difficulty penetrating, limiting root growth, making the tree weaker and more susceptible to being uprooted in the wind,” said Mr. Hung.
He recommends consulting experts in selecting urban trees according to the attached labor norms and standards for each type of tree such as planting on streets, parks, schools in terms of aesthetics, environment, and color. “Currently, the technique of planting large trees has specific criteria and regulations, it is necessary to carefully survey the area and space of each location,” he said.
Red sandalwood tree on Hang Dau street was uprooted. Photo: Ngoc Thanh
Associate Professor Dr. Dang Van Ha, Director of the Institute of Landscape Architecture and Urban Greenery, University of Forestry, said that the tree pot creates an environment to help the tree develop its roots during the incubation process, but when planting in another location, the pot layer must be removed so that the roots can cling to the soil. “Some opinions say that leaving the whole pot intact to plant to keep the soil firm is a wrong view,” he said.
Associate Professor Ha said that according to the natural law, when some trees grow up, their taproots will disappear and develop lateral roots, while some trees develop taproots that go deep into the ground. When exploiting and planting trees in urban areas (mostly large trees), the taproot system is cut off and can only develop lateral roots. The larger the tree, the more roots are cut off because it is difficult to recover the entire root system – this is a common phenomenon with urban trees today.
“Another disadvantage is that the size of trees planted in urban areas is not clear. There are streets where trees are planted with diameters of up to 15-20 cm, which is very dangerous,” he emphasized, adding that small trees with diameters of 8-10 cm should be chosen, but the main root system must be preserved for the trees to grow later.
According to Associate Professor Ha, each urban area has its own characteristics in terms of natural conditions and architectural space structure. Therefore, planning and selecting the right type of plants suitable for the characteristics of each type of landscape space for each urban area is an important factor. Especially for street trees, this type of tree is affected by infrastructure and human factors, so it needs to be closely monitored.
Therefore, Mr. Ha assessed that with urban trees, it is necessary to pay attention from the stage of choosing the species, choosing the size and age when planting, and preparing the surrounding soil to have enough freshness, porosity and ventilation for the roots to develop. “When the surrounding area is cramped, the roots will only develop within a narrow range, while the foliage above is dense, if not pruned regularly, it will easily break when there is a storm,” he said.
Dr. Vu Ngoc Long, former Director of the Southern Institute of Ecology, agreed. He said that when planting trees in urban areas, it is necessary to follow the correct technique for removing the potting soil to help the tree grow with its roots clinging to the soil.
The former Director of the Southern Institute of Ecology said that trees planted on sidewalks in big cities and residential areas mainly have their taproots cut off due to the nature of their roots being deeply embedded in the ground, making it difficult to recover them all. After harvesting the trees, growers apply a stimulant to help the trees restore their root systems.
Dr. Trieu Van Hung, former Chairman of the Vietnam Forestry Science and Technology Association, noted that currently each planting hole is only 1.2 – 1.5 m in size, which is too small compared to the requirements for the growth of the tree’s root system. “The simplest thing is to create a hole that is wide and deep enough for the tree to grow comfortably and then it will be more firmly attached,” he emphasized.
Giang Van Minh Street facing Kim Ma (Ba Dinh), two ancient trees with a root diameter of 1 meter are blocking the way, people cannot pass. Photo: Ngoc Thanh
According to statistics from the Hanoi City Technical Infrastructure Management Center (Hanoi Department of Construction), shade trees in Hanoi are rich and diverse in species with 175 species belonging to 55 plant families. In 12 districts, there are more than 8,000 ancient trees (at least 50 years old or trees with a diameter of 50 cm or more at a height of 1.3 m) including main species such as: malabar, lagerstroemia, cheo, banyan, orchid, lat hoa, lim xet (dark muong), camphor, black muong, milk flower, black star, dracontomelon, sua, xancha, phoenix.