If you enjoy tall flower spikes in backyard borders, for height and structure alongside your low-growing perennials, then I do not think you can do much better than Veronica spp.. Also known as speedwells, veronica plants erupt in colorful flowers from midsummer, oftentimes lasting right up until October or even November.
A few years back, I grew a pale pink variety in a London garden, Veronica spicata 'Heidekind', which produced pastel-colored blooms for much of July and August. Alongside white dahlias (I love the star-shaped Dahlia 'Honka Fragile') and Cosmos 'Pink Lemonade', it was blush perfection.
