Coleus is valued for its vividly colored foliage but is fully capable of producing viable seeds, offering an unpredictable way to grow new varieties. Finding and collecting these seeds requires patience, as the structure holding them is often overlooked in favor of the showy leaves. Understanding the seed’s physical characteristics and location is the first step for any gardener looking to harvest their own supply.
Visual Identification of Coleus Seeds
Coleus seeds are minute, often described as tiny specks, making them difficult to handle without specialized tools. Their small size requires careful attention during collection and sowing.
The shape of the mature seed is typically ovoid or teardrop-like, sometimes presenting as slightly triangular with rounded edges. When viewed up close, the surface is generally smooth and lacks significant texture or ridging. The color is consistently dark, ranging from deep reddish-brown to black or dark brown, contrasting sharply with the light-colored chaff from the dried flower.
Handling the seeds demands precision due to their almost dust-like nature; a single sneeze or puff of air can disperse an entire collection. Gardeners often use the tip of a damp toothpick to pick up and place individual seeds for planting. The small scale is a factor in their germination, as these seeds require light to sprout and should not be buried deep in the soil.
Where Seeds Form on the Plant
Coleus seeds develop after the plant has flowered, forming within the small, dried structures on the flower spikes. The plant produces tall, slender inflorescences that rise above the foliage canopy. These spikes bear small, often pale blue or white, tubular flowers that are inconspicuous compared to the vibrant leaves.
Once the tiny flowers fade and drop, the remaining calyxes, or seed pods, along the stalk begin to mature. Each spent flower leaves behind a minute capsule that houses the developing seeds. The best time to check for seed maturity is in the late summer or fall, depending on the growing climate, when the entire flower stalk has turned tan or brown and brittle.
The seed capsules transition from green to a dry, papery texture as the seeds ripen inside. An indication of readiness is when the pods are plump and completely dry, often before they naturally crack open and release the seeds. This drying and browning process along the stalk signals that the plant’s energy has shifted to seed production, confirming the location for harvest.
Collecting and Handling Seeds
Collecting coleus seeds begins by carefully snipping the flower stalks once they are completely dried and brown. It is important to harvest the stalk before the seed capsules burst open and scatter the seeds. Gathering the stalks into a paper bag or envelope contains any loose seeds immediately after cutting.
The harvested stalks should air-dry further for about two weeks in a cool, dry location to ensure all residual moisture is gone. After drying, the seeds can be extracted by gently crushing or rubbing the dried pods between the fingers over a clean tray or bowl. This action releases the dark seeds from the dried floral material, known as chaff.
To separate the seeds from the debris, the mixture can be poured onto a folded piece of paper and slowly tilted, allowing the heavier seeds to roll away from the lighter chaff. Once cleaned and dry, the seeds should be stored in a labeled paper envelope or a small, sealed container in a dark, cool environment. Proper storage is necessary to maintain seed viability, which typically lasts for one to three years.