T. Sendo, Y. Uno, M. Kanechi, N. Inagaki
Rooftop gardening, one of the methods for urban greening, has many benefits for the environment, economy, and urban landscape. The research for green roof establishment is most prevalent in Germany, but is still under development in Japan. Extensive green roof systems with light and shallow substrates enable plants to grow without significant changes in building structure, but suitable plant species must be selected. Various environmental stresses prevent most plants from growing well in extensive green roof systems. For the establishment of urban rooftop gardening in Japan, information on what kind of plant is suitable for growing on the rooftop where environmental conditions are rather severe to many plant species must be obtained. Today, some species of turf and sedum, which are quite tolerant to dry and hot conditions like rooftops, are generally used as plant species for rooftop gardening in Japan, but they are not attractive for urban landscape. The objective of this study was to identify beautiful ornamental plants which survive and grow well on the rooftop, especially in the summer season in Japan. Five plant species (turf, thyme, sedum, verbena, and marigold) were established on the flat rooftop of the four-storey Agricultural Department building of Kobe University in summer 2005. Each plant species was grown in two kinds of shallow substrate containing perlite or not with intensive or extensive watering (5 L every other day or a week). To evaluate the suitability for rooftop gardening, the rate of plant growth, the ratio of ground cover with plant, the number of flowers and the ability of photosynthesis were measured. With limited watering, only sedum grew well. The other species grew with intensive watering. Marigolds were blown away by strong wind. Verbena and thyme appear to be suitable planting for rooftop gardening because of their eye filling and harvesting benefits. Further, thyme needs little management in comparison with verbena.
Sendo, T., Uno, Y., Kanechi, M. and Inagaki, N. (2007). WHAT KIND OF PLANT SPECIES ARE THE BEST FOR URBAN ROOFTOP GARDENING?. Acta Hortic. 762, 333-340
DOI: 10.17660/ActaHortic.2007.762.31
urban horticulture, heat island effect, extensive green roof, photosynthetic rate, green coverage

Acta Horticulturae