Changes

In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high organic content alternative to be substituted if requested.   

In many proprietary systems the default option for planting medium will be a granular material with very low organic matter content. However, many companies can arrange for a high organic content alternative to be substituted if requested.   

The benefits of 'high organic' media are:

 

#Increased water holding capacity, which benefits both vegetation health and stormwater retention,

#Often lighter weight, even when saturated.

|+ Considerations for using a 'high organic' planting medium

#Increased [[phosphorus]] concentration in runoff water, however this may be mitigated by the reduced runoff volume resulting in a lower loading overall,

#The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats.  

!style="background: darkcyan; color: white"|Disadvantages

|Increased water holding capacity, which benefits both vegetation health and stormwater retention <br>Often lighter weight, even when saturated||Increased [[phosphorus]] concentration in runoff water, however this may be mitigated by the reduced runoff volume resulting in a lower loading overall,<br>The lightweight material is more prone to wind erosion, and this should be accounted for in the initial design, alternatives include erosion control blankets, soil tackifiers, or Sedum mats.

 

Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation<ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. doi:10.1016/j.jenvman.2013.09.014.</ref>; stormwater retention was not improved with this increase in depth <ref>Hill J, Drake J, Sleep B, Margolis L. Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology. J Hydrol Eng. 2017;22(8):4017019. doi:10.1061/(ASCE)HE.1943-5584.0001534.</ref>.

Increasing the depth of planting medium from 10 cm to 15 cm has been shown to benefit the vegetation<ref>MacIvor JS, Margolis L, Puncher CL, Carver Matthews BJ. Decoupling factors affecting plant diversity and cover on extensive green roofs. J Environ Manage. 2013;130:297-305. doi:10.1016/j.jenvman.2013.09.014.</ref>; stormwater retention was not improved with this increase in depth <ref>Hill J, Drake J, Sleep B, Margolis L. Influences of Four Extensive Green Roof Design Variables on Stormwater Hydrology. J Hydrol Eng. 2017;22(8):4017019. doi:10.1061/(ASCE)HE.1943-5584.0001534.</ref>.