The plants used are a mix of those on the homeowners’ wish list and other native plantings that would thrive in the rooftop space. These include ornamental grasses such as blue joint grass (Calamagrostis canadensis), Indian grass (Sorghastrum nutans), Muskingum sedge (Carex muskingumensis) and switchgrass (Panicum virgatum).
Other plantings include orange coneflower (Rudbeckia fulgida), butterfly milkweed (Asclepias tuberosa), longbract wild indigo (Baptisia bracteata), whorled milkweed (Asclepias verticillata), red columbine (Aquilegia canadensis), smooth oxeye (Heliopsis helianthoides), whorled mountain mint (Pycnanthemum verticillatum), nodding wild onion (Allium cernuum) and Short’s aster (Symphyotrichum shortii). “These plants are extraordinarily hardy,” Petty says. “They have to be, given the extremes of the region.”
He adds that these plants also have a lot more winter interest and structure than other, more herbaceous plant choices. “This is important in a region in which winter makes up around half the year, or so it seems,” he says.