The two stonecrops performed well under most conditions, although tasteless stonecrop was stunted by early drought. Ice plant performed erratically and, along with maiden pink, poorly in face of drought during establishment. When subjected to any drought, the herbaceous perennials had the fewest survivors in the expanded shale. The study plants were most affected by substrate depth, except for maiden pink, which responded solely to drought. When subjected to early drought conditions, the herbaceous perennials did not survive in 30 mm of either substrate, or in 60 mm of expanded shale; early drought appeared to be more harmful to plant survival and performance than late drought. Although the stonecrops performed well in 60 mm of substrate when subjected to drought, their performance was superior in the expanded clay compared with shale.
The three most resilient species used in the studysaxifrage pink, white stonecrop, and tasteless stonecropalways produced more shoot biomass with increasing substrate depth, regardless of water availability. A standout performer was saxifrage pink, which had an attractive appearance and persistent flowering habit, making it an excellent choice as a green roof plant.
The experiment illustrates how appropriate species selection in the design of unirrigated extensive green roofs may be directed by factors such as substrate type and depth, as well as anticipated drought conditions. "This experiment revealed the variability among drought-tolerant species to various treatments, as well as the different plant responses to substrate type during drought", concluded the scientists.
|Contact: Michael W. Neff|
American Society for Horticultural Science