Delphinium Galahad Delphinium Cultorum is a herbaceous perennial and one of the most impressive garden flowers. Often grown from seeds Delphinium Galahad is a variety from Pacific Giant Hybrids series, and this spectacular flowering plant can reach 6 feet in height. Attractive clumps of deep-green, textured foliage with sharply-toothed leaves and columns of large, pure-white flowers with a white center make Delphinium Galahad one of the most magnificent perennial flowers to grow.