As we sit in the shade of a large tree with a lush canopy and gaze up at it, the tree appears as a symbol of strength and longevity, firmly attached to the ground by its deep roots. Yet, behind this seemingly peaceful scene lies a daily struggle for survival. Due to climate change and improper care, maintaining healthy greenery is becoming increasingly complex. That is why we need to understand how to properly care for them and recognize the signs that indicate the need for help, as discussed with Professor Milka Glavendekić, PhD, a full professor at the University of Belgrade, Faculty of Forestry, Department of Landscape Architecture and Horticulture.

Regarding the health condition of trees, our interviewee states that it is determined through expert visual inspections. When there is suspicion of damage not visible to the naked eye, special devices such as a resistograph and ultrasonic tomograph are used. Over the past 15 years, pheromones — aromatic substances that insects use to communicate with one another — have been utilized for the early detection of insects that threaten tree health in elements of green infrastructure and forests. Tree health greatly depends on its age, but also on climate change, which creates conditions for the emergence of new and invasive pests. In older trees, rot and attacks by xylophagous insects are common, and without timely remediation, they can threaten vitality, stability, and shorten the tree’s lifespan. Trees in newly established green areas are susceptible to solar radiation, which damages the bark, weakens the tree, and facilitates the growth of rot fungi and secondary insects, causing permanent damage.

Deciduous trees with thin bark, such as maple, ash, and linden, are also sensitive to solar radiation, while conifers, especially pines, are exposed to bark beetle attacks and pathogenic fungi. Over the past decade, new pests have emerged that target pines, cypresses, false cypresses, thujas, junipers, and other coniferous species. Climate change, such as prolonged dry periods or heavy rainfall, further threatens greenery. Therefore, it is essential to assess soil conditions before planting and design suitable drainage and irrigation systems. Maintaining existing green areas implies regular care, fertilization, and protection, especially in the first years of tree growth. Additionally, monitoring new, climate-resilient cultivars necessitates ongoing professional development for landscape architects.

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For trees younger than 30 years that show no visible symptoms of damage, expert inspections every five years are sufficient. For trees older than 60 years with visible damage symptoms, inspections should be conducted at least once a year. If seedlings have been transplanted and nurtured in nurseries for over 20 years and then planted in green infrastructure elements, annual inspections are required for the next five to six years. Seedlings after transplanting may carry hidden diseases or pests that are not immediately visible; the first symptoms appear only after two to four years. This is the most critical period for the application of integrated protection measures, as trees over 20 years of age are increasingly being planted and may carry quarantined, harmful organisms as “stowaways”. Expert inspections should be performed by professionals with at least a master’s or doctoral degree.

In cities where maintenance measures are regularly implemented and damaged trees are removed, damage is significantly reduced. A good example of such practice is the city of Pančevo, particularly through tree care in the Narodna bašta park. The lack of or poor implementation of green space maintenance measures is often the result of insufficient knowledge of ornamental plants, a lack of continuous education, and the employment of unqualified workers. Other problems include labor shortages, inadequate investment, and other challenges.

In most cities and settlements, Public Utility Companies (PUCs) are responsible for the care and health of green areas. They are the first line of defense for early symptom detection and taking appropriate protective measures, and when needed, they seek expert assistance from authorized institutions or private companies. In cities without experts, problems are more complex to detect and are usually discovered too late. As our interviewee points out, citizens also play a crucial role, which is why training programs are conducted to recognize symptoms of certain harmful organisms. Early reporting training was held at the Faculty of Forestry, at the International Horticulture Fair, and in PUCs involved in the care and protection of green infrastructure elements, as well as at the Chamber of Engineers and its branches throughout Serbia. Therefore, it is essential to enhance cooperation among professionals, institutions, and citizens to preserve the greenery that makes cities healthier places to live.

Prepared by Katarina Vuinac