Probably the most critical factor in tree health and longevity is the provision of enough quality soil for the tree roots. When planning trees into urban projects, it is crucial that the target soil volume is established in the early design stages. This will maximise return on your green investments and ensure they grow quickly into large healthy specimens.
Probably the simplest way of calculating a minimum required soil volume is to take the projected canopy area of the mature tree, multiplied by a depth of 0.6 metres. The shape of this area can be configured to suit the particular site.
GreenBlue Urbans's document, calculating target soil volumes, gives four example scenarios:
- small tree pits
- medium tree pits
- medium linked tree pits
- large linked tree pits
Utilising StrataCell structural soil modules installed to the appropriate depth and based on the plan dimensions of each project example can achieve the optimal volume of uncompacted rooting soil.
When tree pits are linked, target soil volumes can be reduced by up to 20% as the roots will ultimately share each other’s soil volume.
GreenBlue Urban also offers an online soil calculator.