36-48" x 48" wide. One of the best Blue Mist Spirea varieties, 'Dark Knight' has the deepest blue color of them all. Its tidy, upright growth habit and profusion of flowering spikes make it an essential part of the summer landscape. A reliable performer, 'Dark Knight' flowers heavily every year. Of modest size, it can be used in front of low walls, as a hedge or in groups around the base of larger shrubs, small trees and upright evergreens. Avoid heavy wet clay soils. Zone 5-9