Green roof systems are now common in many European countries. Aside from aesthetic considerations, these systems present many environmental advantages in urban planning ecology. A flat roof surface (250 m2) was rebuilt on the top of a 30-year-old building. Our objective was to determine the effects of roof microclimate on the growth and development of six herbaceous perennials: Ajuga reptans, Arenaria verna `Aurea', Armeria maritima, Draba aizoides, Gypsophila repens, and Sedum Kamtschaticum. Rooted plants were transplanted into an artificial substrate at three depths (5, 10, and 15 cm) in a 36-m2 area. A special protective covering (Soprafiltre) was installed over the growing area. The following result are presented: temperature variations (winter–spring–summer) at crown and root-zone level, plant hardiness, growth index (height × width), and flowering.
Marie-anne Boivin, Blanche Dansereau and André Gosselin
Marie-Anne Boivin, Marie-Pierre Lamy, André Gosselin and Blanche Dansereau
A green roof system was installed on an existing 35-year-old building. The purpose of the study was to evaluate the effect of three substrate depths on low-temperature injury of six herbaceous perennials: bugleweed (Ajuga reptans), sandwort (Arenaria verna `Aurea'), sea pink (Armeria maritima), whitlow grass (Draba aizoides), creeping baby's breath (Gypsophila repens), and stonecrop (Sedum xhybridum). Plants in 4-inch (9-cm) pots were transplanted into three substrate depths: 2, 4, and 6 inches (5, 10, and 15 cm) and evaluated over a 3-year period. The analysis of the results showed that the species have different winter hardiness, therefore some species were subject to more freezing injury than others. Stonecrop had significantly more damage at 2-inch than 4- or 6-inch depths during the two winters. Bugleweed and creeping baby's breath showed more damage at 2 inches in 1996-97, not in 1995-96. Substrate temperatures were measured from Oct. 1995 to May 1997. Low temperature injury was more pronounced at 2 inch than at 4 or 6 inch depths. Minimum daily temperature and temperature variations measured in fall and spring of these 2 years were also higher at 4- and 6-inch depths.