Acclimatization of Mediterranean Native Sages (Salvia spp.) and Interspecific Hybrids in an Urban Green Roof under Regular and Reduced Irrigation

Abstract

Native-to-Greece sage species, namely, Salvia fruticosa, S. officinalis, S. pomifera ssp. pomifera, S. ringens, S. tomentosa and interspecific hybrids, were evaluated for their acclimatization in an extensive Mediterranean green roof during summer under regular and reduced irrigation (every 2–3 days with substrate moisture 16–22% v/v and 4–5 days with substrate moisture 7–11% v/v, respectively). A substrate (grape-marc compost:perlite:pumice, 3:3:4, v/v) that was 10 cm deep was used. Regardless of the irrigation frequency, S. pomifera ssp. pomifera × S. ringens and S. officinalis × S. pomifera ssp. pomifera showed the highest survival of all hybrids and species, along with satisfactory growth, while S. fruticosa showed the lowest survival. Reduced irrigation resulted in the reduction of aboveground and root biomass, with no damage to the photosynthetic apparatus. S. fruticosa showed the highest (53%) aboveground biomass reduction and S. officinalis, S. officinalis × S. ringens and S. pomifera ssp. pomifera × S. ringens showed the lowest (28, 23 and 3%, respectively), while S. officinalis × S. pomifera ssp. pomifera and S. pomifera ssp. pomifera × S. ringens showed the lowest reduction in root biomass (13 and 16%, respectively). With a reservation for S. fruticosa, Greek Salvia spp. and their interspecific hybrids studied in the present work are recommended for sustainable exploitation in extensive green roofs in arid regions and generally in xeriscaping.