A study was conducted to compare sustainability performance (SP) and visual preference of landscape elements in six professionally designed landscapes. The sites chosen for study provided a range of low to high emphasis on sustainable landscape design. Landscape elements in each site were evaluated for two attributes: SP and visual preference. Sustainability performance was evaluated using the Sustainable Sites Initiative (SSI) scoring system. Visual preferences for landscape elements were assembled by surveying three populations of volunteers: landscape design professionals, landscape design students, and nondesigners (potential residential clients). Few significant differences were observed among the visual preference responses of participant groups. In the few differences noted, we found that the more knowledgeable participants were about landscape element’s ability to improve the environment, the more likely they were to rate them as visually preferred. Average values for SP and visual preference were negatively correlated. However, many individual landscape elements were rated highly in both SP and visual preference. These results suggest it is possible to design landscapes with both highly sustainable elements that are also highly visually preferred.
Compared with traditional roofing, green roofs (GRs) have quantifiable environmental and economic benefits, yet limited research exists on GR plant survival, maintenance practices, and costs related to plant performance. The objective of this study was to assess plant cover, site conditions, and maintenance practices on 10 extensive GRs in the Research Triangle Area of North Carolina. Green roof maintenance professionals were surveyed to assess plant performance, maintenance practices, and maintenance costs. Vegetation cover on each site was characterized. Relationships among plant performance and environmental and physical site characteristics, and maintenance practices were evaluated. Survey respondents ranked weed control as the most problematic maintenance task, followed by irrigation, pruning, and debris removal. No single design or maintenance factor was highly correlated with increased plant cover. Green roof age, substrate organic matter, and modular planting methods were not correlated with greater plant cover. Results showed a trend that irrigation increased plant cover. Plants persisting on GRs included several species of stonecrop (Sedum sp.), but flame flower (Talium calycinum) and ice plant (Delosperma basuticum) were also present in high populations on at least one roof each. Green roof maintenance costs ranged from $0.13/ft2 to $3.45/ft2 per year, and were greater on sites with more weeds and frequent hand watering.