Effect of Artificial Substrate Depth on Freezing Injury of Six Herbaceous Perennials Grown in a Green Roof System

Abstract

<jats:p>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 (<jats:italic>Ajuga reptans</jats:italic>), sandwort (<jats:italic>Arenaria verna</jats:italic> `Aurea'), sea pink (<jats:italic>Armeria maritima</jats:italic>), whitlow grass (<jats:italic>Draba aizoides</jats:italic>), creeping baby's breath (<jats:italic>Gypsophila repens</jats:italic>), and stonecrop (<jats:italic>Sedum xhybridum</jats:italic>). 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.</jats:p>

The relationship between percentage of organic matter in substrate and plant growth in extensive green roofs

“…Generally, green roofs are likely to have greater fluctuations of soil temperature and soil moisture than in a greenhouse, especially thin substrates (Boivin, Lamy, Gosselin, & Dansereau, 2001) because of more frequent irrigation, irregular rainfall, strong wind and high radiation on roofs. In the UK, for example, rainfall is frequent and this would be associated with a greater frequency of the drying and wetting cycle, and hence lush growth with high organic matter content could be a problem.…”

Effect of substrate depth on initial growth and drought tolerance of Sedum lineare in extensive green roof system

“…Fresh mass (g) Dry mass ( fluctuations in temperature (Boivin et al, 2001). However, there are reports with contradictory results in Sedum acre and Arabidopsis thaliana, which showed similar or even bigger plant growth in shallower substrates Olly et al, 2011).…”

“…Deeper substrate also maintains more stable soil temperature and provides larger space for roots of green roof plant. Boivin et al (2001) found that shallower substrates in extensive green roof experience much more severe temperature fluctuations than deeper substrates. However, there are no published studies on the effects of substrate depth on root morphology and distribution and their relationships to plant drought tolerance in green roof.…”

Influence of vegetation composition on runoff in two simulated green roof experiments

“…Virtually all published studies which focus specifically on green roof plants are concerned with plant selection in terms of survival of the environmental stresses of the roof environment (e.g. Boivin et al 2001;Dunnett and Nolan 2004). An exception is the study of Monterusso et al (2004), which tested the influence of four different commercial green roof systems on the quantity of stormwater runoff from that system.…”