Grow Organic Heirloom California Giant Mix Zinnias Organic California Giant Zinnias produce stems as tall as 4 feet with huge 5" blooms, making this variety ideal for cut flowers! The shape of the flower is a bit more open than the Dahlia Flowered variety, with petals rounded on the end. Easy to grow, Zinnias look wonderful when planted "en masse". Plant Zinnia California Giant flower seeds in full sun, in beds and borders for a bright and colorful garden. And then, the more you cut, the more they bloom!