Zinnias are low maintenance flowers that make your garden sparkle with prolific blooms that come on almost every color of the rainbow, and zinnias are also a good nectar plant for bees, butterflies, hummingbirds and other pollinators. Depending on the variety, zinnias can be anywhere from 10 inches to 4 feet tall, making them a good addition to any sunny spot in your garden. It's easy to collect and dry your own zinnia seeds to grow next year. Doing so allows you to choose your favorite colors or to grow seeds saved from the healthiest plants that are best suited for your garden site.
Choose which zinnias you would like to save seeds from. Zinnia seeds sold in garden centers are often a mix of colors, so when you save your own seeds you can choose your favorite varieties, or can separate them by color if you would like to grow red zinnias by the front door and yellow zinnias along the sidewalk.
Wait until the end of the growing season, when the blooms have faded and the seed head have begun to dry on the stalk. The seeds, which can be found in the center of the zinnia flower at the base of the petals, should be brown or green. If they are white or yellow-ish, they are not ready to be harvested. Since goldfinches and other birds like to eat zinnia seeds, you may need to protect the seeds heads while you are waiting for them to dry. You can do this by placing a small paper bag around the seedhead and tying it tight around the stalk with a piece of string.
Snap the seedheads off the zinnia stalk once the seeds have started to dry. You may do this before or after the frost.
Allow the zinnia seedheads to dry in open or very loosely closed paper bags until the seeds are completely dry and brown. Depending on how dry your zinnia seeds were when you picked them, this could take a few days or a few weeks. With a pen or pencil, label each bag with the color or variety of zinnia inside of it.
Brush your finger across the seedhead to loosen the seeds. Zinnia seeds are very small and are oblong or arrowhead-shaped.
Store your zinnia seeds in labeled paper bags or envelopes and keep them in a cool, dark place until spring. Paper storage allows for air circulation and helps the seeds dry out over the winter. Zinnia seeds do not need to be refrigerated, but they should be kept away from any heat sources. A root cellar or basement is ideal.