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What Does An Urban Tree Need To Survive?

Urban tree planted outside Richmond centre in Derry.

Planting a tree in an urban environment involves a huge change of habitat to that of a tree living in the freedom of a forest, so what does an urban tree need to survive?

For any tree to survive, it needs access to:

  • Sunlight – The catalyst for photosynthesis
  • Water – Trees are on average 50% water. It is needed to fill growing plant cells and hold the tree upright. Water is also a product required for Photosynthesis, a means to distribute nutrients to parts of the tree and the substance which a tree uses to moderate its temperature.
  • Nutrients – So that it grows healthy and strong in order to resist pests, disease and stress.
  • Space – Room for growth, both above ground for its canopy to spread out and below for loose rooting volume in which a tree can anchor and support itself.
  • Air – CO2 is required for photosynthesis. Soil also needs to be aerated to allow for gaseous exchange to the roots and to maintain nutrient levels in the soil.

Let’s now compare a trees natural rural environment to that of the urban location.


  • Sheltered microclimate
  • Rich fertile soil with an abundance of nutrients, humus and uncompacted leaf mould
  • Rich rooting volume with plenty of moisture and pore space
  • Harsh paved surround
  • Increasing microclimate temperatures and reflected glare
  • Exposure to wind, de-icing salt and vandalism
  • Compacted soil and lack of quality rooting volume
  • Competition for space with multiple utilities and foundations
  • Even if a tree does manage to spread its root system it can still be endangered by trenching or pavement reinstatement

We cannot entirely recreate the conditions trees enjoy in the woodland however we can hugely improve their chances of thriving by paying attention to the trees needs and putting a solution in place.

Solutions to the urban tree planting problem
Direct the roots downwards
Using root directors to deflect tree roots downwards whilst they are growing results in multiple benefits:
  • Improves tree stability and anchorage
  • Encourages deep root growth for greater drought tolerance and resilience to de-icing salt
  • Prevents root heave to surrounding surfaces such as pavements
  • Protects subsurface utilities from damage caused by roots
  • Prevents root girdling
  • Irrigate the soil at the root level
    Surface irrigation is inefficient as water scarcely penetrates the surface and only encourages shallow root growth. By introducing an irrigation system located at the root zone and accessible by an inlet, water can be delivered without wastage to the desired level wherewith to encourage deep root growth. Such systems also offer an access means for air and feeding with soluble feeders.
    Provide a large volume of quality uncompacted soil
    Here arises a conflict of interest because although a tree needs loose soil in which to establish its roots, a trafficked urban environment requires a solid and stable foundation if its to be paved or tarmacked. As such, there are some ingenious soil support products on the market to overcome this problem. Typically, they are ridged plastic structures with an open lattice designs so that when interlocked together they can not only support huge weight loads, but protect the loose soil they contain.  

    So in summary, is it worthwhile investing in urban trees? The answer is yes, so long as you invest in a supporting system that facilitates the trees growth. Their success in investment below ground, will manifest in their canopy above ground over time.

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