In cities, trees are essential green infrastructureA successful selection minimizes conflicts with services, roads and buildings, and maximizes environmental and social benefits such as shade, thermal comfort, biodiversity and well-being. Choosing well means understanding that the tree is a living organism with requirements of space, soil, water, light and long-term management.
Site selection and environmental assessment
Before thinking about species, define the place. The urban context is complex and busy: There is competition for space with underground and overhead networks, traffic visibility, and regulations. Consider permits and professional advice whether it is public or private space.
Urban land is usually a “made soil”: An anthropogenic mixture, sometimes poor in structure, organic matter, and biology. Analyze texture, pH, salinity, and contaminants. Prioritize soils. permeable and aerated; if there is compaction, use decompaction with air injection/air spade and improve the profile with stable organic matter.
Value restrictions and opportunities: building shading, wind channeling between towers, heat islands, ponding, or runoff. In new developments, design the “right place for the right tree”: Size rooting volumes and soil structures that support traffic without sacrificing roots.
Selection criteria for urban species
Define criteria on four axes: site suitability (cup and root space, light, wind, soil), Ecosystem services (shade, biodiversity), unwanted services (pollen, fleshy fruits, aggressive roots) and resilience (drought, frost, pests). Deciduous trees favor winter solar gain and summer shading; evergreens reduce clean-up tasks. Conifers can limit the understory on lawns.
calculate the adult size: The root projection usually approaches the crown. In dense rows, use “V” shaped crowns and a clear base to coexistence with wiring and traffic. Avoid species with fleshy fruits that dirty sidewalks or with hairy leaves that collect dust. Prefer roots non-invasive in environments with pavements and services.
Light conditions architecture: with high facades, trees tend to to etiolate; select species tolerant of partial shade or redesign spacing. Water is critical for establishment; adults deepen roots toward surpluses and groundwater, but young plants require regulated irrigation.
Prioritized ecosystem services
For air quality, think “reduce, separate, protect”: reduce emissions with active mobility, separate pedestrians from sources and create green oases. To capture particles, cups with large leaf area, porous density that allows air flow, leaves with micro-roughness and leaf permanence. In gases, the stomatal conductance healthy is key.
The trees lower temperatures by shadow and evapotranspiration. Large canopies are more effective than other green infrastructure in cooling neighborhoods. Integrating trees into sustainable urban drainage helps reduce heat waves and improve the quality of life in public spaces.
Biodiversity and genetic diversity
All trees provide habitat; increase the gender diversity to sustain more wildlife. Use the rule 10-20-30: no more than 10% of a species, 20% of a genus, and 30% of a family in the urban population. Avoid invasive and value non-invasive cultivars that provide resilience.
The native vs. exotic debate requires pragmatism: natives well adapted to the territory can fail in the city due to thorns, slow growth or allergies; exotic ornamentals are domesticated for urban uses. Select for urban performance, not origin, and support nursery development. urban natives when feasible.
Acquisition, nurseries and biosecurity
Implement purchasing policies with seed-plant traceability, post-import insulation and material preference locally producedCultivation contracts anticipate sizes and qualities required. Prioritize low pollen load in sensitive environments and species with attributes of PM filtering.
Planting, establishment and maintenance
Prepare the ground according to the production system: bare root, root ball, container or containerizedAvoid settling the tree below the root collar; in clays, break side walls of the hole. For large cups, design volumes of structured soil and aeration; the Stockholm type solution integrates structural gravel and fertile soil.
For 3–5 years, monitor weeds, water regularly and use wood chip mulch (better monospecific for its fungal effect). Avoid fertilizers when planting. formative pruning Early intervention creates a stable architecture (dominant leader, base clearance on streets) and reduces future risks.
Risk prevention, monitoring and management
Strengthen the pest and disease surveillance with monitoring and citizen science programs. Design decisions retention and logging transparent and participatory, prioritizing the conservation of valuable trees and planning replacements.
In works, prepare a Tree Protection Plan: BEA (tree effect analysis), root protection zones, fences and walkways anti-compaction, trial trenches, excavation by air/vacuum near roots, and scheduling that minimizes water stress. Monitor with a arboriculture expert and carry out soil recovery measures after the construction.
Suggested selection according to context
Parks and squares: species long-lived and large for structure and chromatic diversity; Small/medium streets: crowns tall and “V” shaped, non-invasive roots and low dirt; Avenues: bases clear and cylindrical crowns; Intersections and road junctions: trees robust tolerant to compaction and heat.
Rigorous planning, proper selection and adaptive management allow urban trees to fully develop their potential. Maximum capacity, providing thermal comfort, landscape identity and public health; with adequate space and care, the urban forest becomes more resilient and secure in the face of droughts, heat waves and health pressures.
