There are many mounding plants, but they need to be interspersed in a garden with some vertical accents.
One native plant that produces vertical flower spikes is liatris (LYE uh tris) zones 3 to 9, which has the two common names of blazing star and gay feather.
The flower spikes, produced in summer, are unique because the florets open from the top down, instead of from the bottom up, and they are a magnet for bees and butterflies. The foliage creates a soft grass-type clump. Liatris plants are valuable perennials in beds and borders, and the flowers can be lavender, rose, purple or white and are good cut flowers in a vase. Grow these beauties from bulbs that are planted in the spring.
Another plant with vertical interest is kniphofia, which has the common names of torch lily and red hot poker and grows from rhizomes. This South African native produces poker-shaped flower heads covered with tightly massed tubular flowers that hummingbirds love. They bloom August-October in zones 5 to 8.
Foxtail lilies from Afghanistan (zones 4 to 8) and pineapple lilies (zones 5 to 20) from South Africa are other plants with flowers that create exclamation points in a border.