Salt tolerance of common green roof and green wall plants

Detrimental effects of road deicing salt on vegetation are well known and have been well studied, with the exception of typical green roof plants, which could experience damage on green roofs with public access and green walls near roadways in cold climates. Two studies were conducted comparing salt tolerance of five Sedum species, two Allium species and a mixture of turf grasses when exposed to six levels of salinity applied either as foliar spray or as liquid applications to the soil. A third study compared salt tolerance when plants were placed at three distances from a major highway. Response variables measured included survival, a health score from 0 to 5, and a growth index. Allium cernuum, A. senscens and S. ellecombianum were relatively tolerant of both saline spray and soil inundation at high saline concentrations in terms of survival, mean health scores, percentage of healthy plants and growth index. Sedum reflexum was much less tolerant of saline spray at higher salinity concentrations and soil inundation regardless of salinity levels. Distance from the road had no effect on plant survival rates but plants farthest from the road had higher mean health scores and a greater percentage of healthy plants than plants closer to the highway.