ReviewSubstrates for cultivating herbaceous perennial plants in extensive green roofs

Substrate is one of the most important components in the cultivation of extensive green roofs. However, there is still a lack of information on the effect that components of the substrate have on vegetation growth. Also, most substrates used in the commercial production of ornamental plants have a density superior to the adequate for these cultivations. The local availability of materials and features such as porosity and water retention capacity are essential when choosing the composition of the substrate that will be used in a green roof. This study aims to develop and recommend substrates for extensive green roofs in the southern region of Brazil. Fifteen samples of substrates with different compositions were developed. Based on their physical and chemical properties, four samples were chosen and used for cultivating two plant species, Sedum acre Lineu and Arachis repens Handro, both perennial herbaceous plants recommended for this type of practice. The experiment was carried out at the Experimental Studies Center of the Federal University of Paraná - UFPR (latitude: 25°39′41″S, longitude: 49°11′41″W, altitude: 895 m), from November 2014 to November 2015. The cultivation was performed over physical modules with wooden structures similar to a conventional roof, covered with fiber cement tiles and with a 5% inclination. Photographs were taken every 15 days for the determination of degree of vegetation coverage. For both species, the substrates comprised of sawdust and poultry manure had a larger vegetation ground cover (GC) however, S. acre did not tolerate excessive rainfall, and therefore is not indicated for isolated usage (monoculture) in regions of subtropical climate. Nevertheless, this species reached almost 100% coverage in higher temperatures and during a longer period. A. repens had GC around 80% in rainy periods, thus is indicated for cultivation in such conditions.