Periwinkles (Catharanthus roseus) reach heights of 24 inches and bloom year-round with white, pink or purple blossoms. These drought-tolerant perennials are hardy in USDA zones 9b to 11 and prefer sunny, well-drained sites. Tiny rain lilies (Zephyranthes spp.) grow from 4 to 12 inches tall and bloom from spring through fall. Hardy in USDA zones 7b to 11, rain lilies tolerate a range of soil types and some salt spray.
White gauras (Gaura lindheimeri) produce delicate white flowers that resemble butterflies. Though these perennials may look fragile, they tolerate drought, a range of soil types and thrive in sunny sites. White gauras grow to 3 feet tall and are hardy in USDA zones 8 to 9. Blazing star (Liatris spp.) also grows to 3 feet tall and prefers sunny exposures. Blazing star blooms with tall spires of white flowers in summer, attracting bees and butterflies to the yard. It's hardy in USDA zones 8 to 10.
The African iris or butterfly iris (Dietes vegeta) grows up to 6 feet tall when planted in standing water -- less in soil -- and produces 3-inch-long white flowers year-round. Hardy in USDA zones 8b to 11, these perennials prefer sandy, slightly acidic soil. Reaching up to 5 feet, the butterfly ginger (Hedychium coronarium) blooms with aromatic white flowers in late spring and summer. This perennial is hardy in USDA zones 8b to 11 and prefers moist planting sites.
For dramatic vertical interest and white flowers, plant bluestem grass (Andropogon spp.) This low-maintenance perennial grows up to 10 feet tall and blooms with white-silver flowers in autumn. A Florida native, Bluestem grass is hardy in USDA zones 8 to 10 and tolerates salt spray, drought and a range of soil types and pH levels. Rising even higher at 10 feet tall, pampas grass (Cortaderia selloana) thrives in sunny, dry sites. Hardy in USDA zones 5b to 11, pampas grass blooms in summer with large, plumed white-silver flowers.