Arctostaphylos uva-ursi (Kinnikinnick) is an obvious prospect for a green roof. Attractive, tolerates water-logging and drought, and found throughout the Pacific Northwest. The problem is that it grows slowly and is not easily transplanted. If you are planning to grow it for yourself it would seem best to start with cuttings or seed. This web site gives information on propagation from seed, stem cuttings and root cuttings. The Woodland Park Zoo tested Kinnikinnick on a green roof in 2006. They found that it survived but only on slopes of less than 15%. At greater slopes their growth medium (6 inches in depth) did not retain water well enough to prevent root drying. Some details are given in a Masters degree thesis. The Kinnikinnick plants were young and perhaps had not established an extensive root system. I advise you to call ( (206) 548-2520) or drive to the zoo and find out more recent information. Kinnikinnick has also been used on the Vancouver, BC, library roof.
Because of the widespread interest in green roofs improved planting media are always appearing. I found numerous potentially useful web sites in a Google search for "Green roof growth media, Pacific Northwest. Kinnikinnick plants are available in Seattle area nurseries, e.g., the Woodbrook Native Plant Nursery and probably at some of the ones on this list.
