What we did
We supplied 48 of our sedum cassettes. Each cassette contains four key layers; the base is a drainage layer of expanded clay granules, which slows water filtration without water-logging, as well as holding on to some moisture within its micro-pores. Above this sits a filter layer; a geo-textile that allows the passage of water, but no substrate particles which could block the drainage holes. Then sits the substrate itself, which has been specially blended to meet the needs of the sedum, offering nutrients, moisture, and anchorage to the plants above. Finally, the sedum itself, a mix of up to 16 species. Each cassette offers near 100% coverage, which gives instant impact once the cassettes are laid.
Measuring just under half a metre square, each cassette connects to the adjoining unit, making installation both simple and extremely quick. Once laid, these are relatively maintenance free although we would recommend you remove any weeds or dead foliage in the spring and autumn, and a quick check to ensure that the drainage holes are clear. These really are a “lay it and leave it” solution to adding more green to our urban commuter routes.