Effects of plant density and cutting-type on rooting and growth of an extensive green roof of Sedum sediforme (Jacq.) Pau in a Mediterranean environment

Species of the Sedum genus are a popular choice for green roofs as they thrive in shallow growth layers and are resilient to extreme environmental conditions; they are also easy to propagate from seed, plantlings or plant parts. The use of rooted cuttings is most widespread due to good rates of establishment. In the interest of cost reduction, the direct spreading of Sedum cuttings over the roof area, especially over large areas, has attracted attention in recent years. Considering the interest on the above method and the seeming lack of experimental data available, this study aims to further knowledge in this area. Experimental tests on direct spreading of unrooted cuttings of Sedum sedifonne (Jacq.) Pau were carried out in order to study the effects of plant density and cutting-type both on rooting and on the growth and cover dynamics in a green roof simulated on the ground. The results highlight that tip cuttings responded more quickly to rooting and with higher percentages compared to node cuttings. However, node cutting, when used at greater density, created more continuous plant cover in a shorter period of time.