Trevor Dixon
Summary
Urbanization has led to increased impervious surfaces, reduced green spaces, and rising temperatures in cities. To counter these challenges, the implementation of podium gardens, elevated green spaces on building podiums, has gained popularity. This report explores the benefits and considerations of planting trees in podium gardens, with a focus on urban sustainability.
Introduction
Podium gardens, situated atop buildings or parking structures, offer an innovative solution to urban green space limitations. Integrating trees into these elevated gardens can significantly contribute to environmental sustainability and enhance the overall well-being of urban communities.
Benefits of Planting Trees in Podium Gardens
Air Quality Improvement. Trees act as natural air purifiers by absorbing pollutants and releasing oxygen. Podium gardens with trees contribute to the reduction of particulate matter and other air contaminants.
Temperature Regulation: The shading effect of trees helps in reducing the urban heat island effect, mitigating high temperatures in densely populated areas. Improved microclimates in podium gardens positively influence building energy efficiency.
Biodiversity Enhancement: Trees attract and support a diverse range of wildlife, promoting biodiversity in urban environments. Podium gardens with trees create miniature ecosystems that can support various plant and animal species.
Aesthetic and Psychological Benefits: Greenery and trees contribute to a visually appealing environment, fostering a sense of well-being among residents. Exposure to nature has been linked to reduced stress and improved mental health.
Considerations for Tree Planting in Podium Gardens:
Structural Considerations: Structural engineers must assess the load-bearing capacity of podiums to ensure they can support the weight of mature trees and their root systems. Proper drainage systems should be incorporated to prevent waterlogging. This includes waterproofing membranes, correct falls to drainage outlets as well as physical protection with geofabric, corflute and preferably drainage cells (instead of drainage gravel) to keep drains operating correctly.
Tree Selection: Choose tree species that are well-suited for urban environments, considering factors such as soil quality, wind resistance, and available space. This also includes other factors such as the impact in strata title developments where desirable views can be restricted in properties above ground level; this also works in reverse where privacy may be considered the dominant preference and taller species should be planted.
Growth patterns and potential size of the selected trees to avoid conflicts with surrounding structures. Consider the size of root balls and spreading nature of roots in some species that may seek out water sources such as Ficus sp. These may expand through micro fissures to eventually disrupt water proofing infrastructure. Larger trees will also invariably spread their roots over time and can still cause these problems.
Maintenance: Implement a robust maintenance plan, including regular pruning, watering, and pest control, to ensure the health and longevity of the trees. Involve professionals in the planning and maintenance process.
Conclusion
Planting trees in podium gardens is a sustainable and innovative approach to addressing the environmental challenges associated with urbanization. With careful planning, selection, and maintenance, podium gardens can contribute significantly to urban sustainability, creating healthier and more vibrant urban spaces. Integrating greenery into the urban landscape not only enhances the quality of life for residents but also contributes to a more resilient and sustainable urban future.
Where maintaining views and minimising impact on waterproofing is the primary consideration, the selection of dwarf varieties of trees is recommended. Hard crown pruning of established trees is difficult as it rarely produces an outcome where the shape of the tree re-establishes itself satisfactorily and they ultimately “look wrong”. The ideal solution is to do it right the first time, however mistakes do happen and removing poor choices is expensive and heartbreaking to see the removal of mature trees.
