Zinnias are popular annual flowers that produce abundant blooms throughout the warm season. Gardeners often save their own seeds from these plants. As the growing season concludes, the vibrant petals dry and fade, signaling the time to harvest the next generation of plants. Seed saving involves sifting through the brittle, dried flower heads to isolate the small, mature seeds needed for the following year’s garden.
The Anatomy of a Zinnia Flower Head
A zinnia bloom is a composite flower head, not a single flower. This structure is composed of two distinct types of smaller flowers, known as florets. The showy, colorful parts that resemble petals are technically called ray florets.
The center of the bloom is made up of numerous tiny disc florets, which are often yellow or brown. Viable seeds develop at the base of both the ray and disc florets. Once the flower dries completely on the stem, the entire head becomes a brittle casing holding the matured seeds.
Identifying Viable Zinnia Seeds
A viable dried zinnia seed has a distinctive appearance, often described as an arrowhead, spearhead, or spade shape. These seeds are small, elongated, and flattened. They are typically found attached to the base of the dried ray floret, or petal. Viable seeds are firm and feel solid to the touch, indicating a fully developed embryo inside.
The color of a mature, viable seed is reliably dark, ranging from dark gray to black. This dark coloration indicates maturity and proper drying on the plant. While some seeds may display light streaks or tips, the majority of the seed body must be dark. Immature seeds harvested too early will appear pale, white, or moist and are unlikely to germinate.
The seed produced by the ray floret tends to be the recognizable spade-shaped structure. Seeds from the central disc florets can sometimes be smaller and more irregularly shaped. Regardless of origin, a good seed maintains a hard, rigid structure. If the seed is dark and resists being easily crushed, it is a good candidate for saving.
Distinguishing Seeds from Non-Viable Material
When a dried zinnia flower head is crumbled, the resulting material is a mixture of seeds and dried flower parts called chaff. Separating the two relies on the difference in weight and texture. The non-viable material consists of brittle, papery petal remnants, empty seed casings, and undeveloped, pale seeds.
Viable seeds are dense, heavy, and dark, having a higher mass than the surrounding debris. Gardeners often use a technique called winnowing to separate the seeds, which relies on this weight differential. This involves gently shaking or blowing across the collected material. The lighter, non-viable chaff lifts and blows away, while the heavier, dark seeds remain behind.