LAUSR

This study aimed to determine the effects of different amounts of hydrophilic polymer, in three green roof substrates, on the growth of Salvia elegans. Coir dust and perlite were mixed in ratios of 80% to 20% (C4P1), 50% to 50% (C1P1), and 20 to 80% (C1P4) at a substrate depth of 20 cm. Hydrophilic polymer were added to three substrates in the amounts of 0, 0.25, 0.5, 1.0, and 2.0 kg·m. The survival rate and visual quality of Salvia elegans were positively associated with hydrophilic polymer content in the three substrates. Although the growth of Salvia elegans was the greatest under the C4P1 substrate when measured in June (dry season), the greatest growth under the C1P4 substrate was in August (rainy season). Therefore, C4P1 and C1P1 substrates with high coir dust materials is not recommended for Salvia elegans because the plants showed low growth and chlorophyll contents in the rainy season and poor flowering with these substrates. Thus, perlite-based C1P4 amended with hydrophilic polymer at a level of > 1.0 kg·m should be considered for the optimal substrate for Salvia elegans during droughts as well as rainy seasons on green roofs.