Assessment of perlite, expanded clay and pumice as substrates for living walls

Vertical greening systems for buildings are becoming common in many cities. There are different options in the market but some types of living walls require the use of inorganic substrates as plants are grown in a hydroponics culture. In this study, three different substrates (expanded clay, perlite and pumice) are tested in six living wall modules (two per substrate) with two lighting conditions. The substrates were physically and chemically characterized and both water consumption and plant development (green cover, flowering, biomass production and photosynthetic activity) were monitored in two different tests. The three substrates showed to be suitable for living walls and most of the differences observed were due to the lighting conditions. Among the three substrates assessed, pumice exhibited a slightly better performance in terms of green cover and biomass production.