The Growth of Arthrocnemum macrostachyum and Halimione portulacoides in an Extensive Green Roof System under Two Watering Regimes

The marine halophytes Arthrocnemum macrostachyum and Halimione portulacoides are found growing naturally in saltmarshes within Greece creating an aesthetically pleasing groundcover that also reflects the changing of seasons. The potential use of these species in an extensive green roof system in coastal areas would lead to additional benefits such as preserving and enhancing the local landscape character and supporting biodiversity. The growth of Arthrocnemum macrostachyum and Halimione portulacoides in an extensive green roof system under two watering regimes (30% ET0 and 15% ET0) was investigated. The substrates used consisted of soil (S), pumice (Pum) and grape marc compost (C) or peat (P), at various volumetric proportions indicated by the subscripts: S15:Pum70:C15, S15:Pum70:P15 and S15:Pum70:P7.5:C7.5. Biometric measurements to determine plant growth included plant height and diameter, growth index, dry weights and ground cover. The growth of both plant species was similar under both watering regimes until elevated summer temperatures lead to plant loss in the reduced watering regime (15% ET0). Both shoot and root dry weights of both plant species at the end of the experiment were greater under the 30% ET0 watering regime. Results indicated that both watering regimes (30% ET0 and 15% ET0) studied could be applied initially in the early summer months followed by watering with 30% ET0 at increased summer temperatures.