Zinnia elegans. California Giants Mix Zinnia seeds form bushy plants that carry masses of huge, 12-15cm (5-6") wide, double flowers in brilliant hues of red, yellow, orange, lavender, maroon, violet, and white. Growing to a height of up to 1m (36"), these plants have a very bold visual appeal. Plant Zinnias in big groups whenever possible, as mass plantings look fantastic. Deadhead spent flowers as needed to keep the bloom period longer. Despite their elegant look, Zinnias are fairly tough plants and are drought tolerant enough to be used in xeriscaping projects. Zinnias are, of course, notable as cut flowers.