Plant Blue Cardinal Flower in spring or early fall in a location with full sun to partial shade. Ensure the soil is consistently moist and rich in organic matter. Space plants about 12-18 inches apart. Water regularly, especially during dry spells, to maintain soil moisture. Fertilize with a balanced, water-soluble fertilizer in early spring. Deadhead spent flowers to encourage more blooms. Divide clumps every 2-3 years in early spring to maintain vigor.