Abstract
We measured evapotranspiration rate of several rooftop gardening plants in order to obtain basic data to quantify the effects of rooftop gardening on thermal environment of the building. We set up rooftop gardens with 2 kinds of soils, natural soil (Andisol) and artificial potting soil (Perlite-based commercial product), in 3 different thicknesses (7cm, 14cm and 21cm). Three species each of common gardening plants that are suitable to each soil thickness were selected and grown in stainless steel Lysimeters buried in the experimental plots. The decrease in weight of Lysimeters was measured as evapotranspiration rate. Evapotranspiration rates of several plants planted at natural soil plots were less than those of the same species planted at artificial soil plots since their conditions were bad. Evapotranpiration rate of Verbena × hybrida planted at natural soil plot was less than the amount of water evaporation from bare soil. In August, the transpiration rates of Rosmarinus officinalis L. planted at artificial soil plot was 7.2 kg/m2/day, that of V. × hybrida planted at artificial soil plot was 12 kg/m2/day, and that of Rhododendron pulchrum Sweet cv. Oomurasaki was 14 kg/m2/day. Those were the highest rates at the plots of each thickness.
