Lobelia - These trailing plants flower prolifically in spring and fall, almost covering themselves in flowers. Annual lobelia is a cool-season plant that does best in shade in the South, though it loves partial shade in the North.
Geranium Rozanne -this is one of the best perennial geraniums around. It makes in height and in spread with a somewhat lax habit. It bears abundant mauve-blue flowers from June-September and likes a well-drained position in sun or partial shade