Plant red valerian (Centranthus ruber) for red, white and pink blossoms that complement the pyracantha's white spring flowers. This 3-foot-tall perennial grows best in full sun and well-draining soil. It's hardy in USDA zones 5 to 8 (ref. 5). For spires of colorful blossoms in late spring, plant bearded tongue (ref. Penstemon spp.) with your pyracantha. This 3-foot-tall perennial blooms with red, orange, white and pink flowers and thrives in full sun and well-draining soil. Penstemon is native to the southwestern U.S. and is hardy in USDA zones 5 to 8.
The coneflower (Echinacea augustifolia) grows well with the pyracantha (ref. 1). Native to meadows across North America, this perennial blooms with pink, purple and white flowers with copper-orange centers in early summer. Coneflowers grow from 3 to 6 feet tall and attract pollinators. They're hardy in USDA zones 4 to 9 and prefer sunny sites with well-draining soil. Sage (Saliva spp.) complements pyracantha with its aromatic foliage and variety of colorful flowers. Sky-blue sage (Saliva uglinosa) grows to 6 feet tall and blooms with light blue flowers in summer. This perennial is hardy in USDA zones 6 to 10 and grows well in full sun and well-draining soil.
For bright yellow blossoms that complement the pyracantha's dark green foliage, plant "Moonshine" achillea (Achillea x "Moonshine"). This perennial hybrid grows to 18 inches tall and blooms in late summer with wide clusters of tiny yellow flowers atop aromatic, gray-green foliage. It's hardy in USDA zones 3 to 8 and prefers sunny, well-draining sites. The black-eyed Susan (Rudbeckia fulgida) also blooms in late summer with yellow flowers. Its daisy-like, golden blossoms have dark centers. Reaching heights to 3 feet, this native North American perennial is hardy in USDA zones 3 to 9 and thrives in full to partial shade and well-draining soil.
The Mexican hat (Ratibida columnifera) blooms with yellow and brown flowers atop long, thin stems from summer through fall. This native perennial is hardy in USDA zones 3 to 10 and grows well in sunny, well-draining sites. It reaches heights of 3 feet and attracts butterflies to the garden. "Indigo Spires" sage (Salvia x "Indigo Spires") blooms from early summer through autumn with 15-inch-tall spires of deep purple blossoms. Hardy in USDA zones 7 to 11, this hybrid thrives in full sun to light shade and well-draining soil. It grows to 4 feet tall.