Cosmos flowers are popular, easy-to-grow annuals that produce a prolific display of daisy-like blooms throughout the summer and fall. These plants are known for their feathery foliage and vibrant colors, making them favorites in cottage and cutting gardens. Understanding how to identify and handle their seeds is the first step toward ensuring a fresh supply of these cheerful blossoms for the following growing season.
The Physical Characteristics of Cosmos Seeds
A cosmos seed is distinct in its appearance. Its shape is elongated, tapered, and slightly curved, often resembling a miniature, slender sword. This slender, oblong form makes the seed approximately 5 to 6 millimeters in length, comparable to a small grain of rice.
The color of a mature cosmos seed typically ranges from black to deep, dark brown, or sometimes a grayish-tan shade. Color variation can occur depending on the specific species, such as Cosmos bipinnatus or Cosmos sulphureus, but the dark hue is a reliable indicator of ripeness. When examined closely, the surface of the seed is often marked with fine lines or ridges that run along its length. These markings contribute to the dry, somewhat brittle texture of the seed, which should feel firm when gently squeezed.
Locating and Collecting Seeds from the Plant
Cosmos seeds develop within the spent flower heads after the petals have faded and dropped away, requiring the seed head to completely dry out on the plant to reach maturity and viability for collection. A mature, ready-to-harvest seed head will look brown, brittle, and fully dehydrated, contrasting with the green, living parts of the plant.
The proper time for collection is on a dry, sunny day, well after any morning dew has evaporated. The dried flower receptacle holds the seeds loosely, and a gentle touch is often enough to make them fall out. You can easily remove the entire dried head from the stem with a simple snap. The seeds are not contained within a hard pod, meaning they are exposed and shed easily once the flower head is ready.
Storing and Preparing Seeds for Planting
Once collected, the first step in preparing the seeds is to ensure they are completely dry to prevent mold and rot during storage. The seeds should be spread out on a screen or a paper plate for several weeks in a dry location, away from direct sunlight. A fully dry seed will feel brittle and snap rather than bend when tested.
After drying, it is important to remove any remaining chaff, which is the dried flower material and debris mixed in with the seeds. Storing the seeds in a clean, airtight container, like a glass jar or a sealed paper envelope, helps maintain their viability. The container should then be kept in a cool, dark, and consistently dry location, where the seeds can remain viable for up to five years. For planting the following spring, the seeds are generally direct-sown outdoors after the last expected frost date.