Beginner Gardening: Flowers for Terrance Wall, 1 by HoosierGreen

HoosierGreen wrote:
For constant bloom, you should try 'Rozanne' perennial geranium. It spreads out to at least three feet by midsummer and will cascade nicely, although it dies back to the crown every winter (unlike other perennial geraniums, it doesn't spread by stolons). Blooms from late spring to hard frost.

I would also recommend using a few spreading junipers for evergreen interest. Even the lowly 'Blue Rug' makes a gorgeous cascade of branches which would break up all that wall year-round.

Another nice wall shrub is Cotoneaster apiculata (Cranberry Cotoneaster) (see the photo) or the harder to find C. horizontalis (Rockspray Cotoneaster) 'Hessi'