Plant Medium For Living Roof

For the best green roof medium the growing media should contain the following.

Plant medium for living roof.

Carex nigra is technically considered a sedge and is often used on living roofs because its roots require less soil than most other grasses or grass like plants. These materials are available throughout the west coast of north america. Not only is it bulky and heavy it can have potential chemical and pathogen contaminants and if not screened may contain rocks or debris that may make the product inconsistent. These aggregates make a good basis for a growing medium.

As well as affording excellent ground cover this hardy easy to maintain plant grows happily in a shallow layer of substrate minimising the amount of pressure it puts on a structure. Soil s saturated weight can reach 120 lb ft 3 7 5 kg m 3 which is far too high for roof gardening. Succulents are plants that store water in a part of the plant. The natural properties of sedum make this succulent plant extremely suitable for roof greening.

The targeted saturated weight of roof top growing media should be 48 65 lb ft 3 3 4 kg m 3. Now comes the growing medium which for a sedum roof should be at least 8cm 3in deep and for a roof of wildflowers herbs salad and strawberries at least 15cm 6in deep. Lightweight volcanic aggregate such as pumice or lava. An all purpose soil less peat free potting mix is fine for growing herbs and other edibles but mix in plenty of perlite to both improve drainage and save on weight.