Butterfly Bush, Black Knight Butterfly BushBlack Knight Butterfly Bush is a well branching shrub with a spreading, arching habit that can reach 6 8 tall if not cut back in late winter. Black Knight Butterfly Bush has willowy grey green leaves and large fragrant spike like clusters of deep, nearly black, purple flowers that bloom in summer attracting butterflies. Removing spent flowers can encourage continued blooms until frost. Best performance in sunny well drained areas. Type: Shrub Origins: