Zinnia Seed Saving Hack for Endless Blooms In fall, let zinnia flower heads dry on the stem until they turn brown and papery. 狀 Collect enough dried heads to fill a small box like a shoebox. Store them in a cool, dry place over winter. In late spring, crumble the dried flower heads and scatter the seeds in rows. Soon, a fresh wave of colorful zinnias will bloom beautifully, just like before! Easy, budget-friendly, and a wonderful way to keep your garden full of color year after year.