The genus Lobelia is celebrated in horticulture for its vibrant blooms, such as the Cardinal Flower (Lobelia cardinalis) or the Edging Lobelia (Lobelia erinus). While the flowers are familiar, the seeds are often overlooked. Lobelia seeds are a remarkable example of botanical miniaturization, which is a significant factor in propagation. Understanding their physical nature is key to successful cultivation from scratch.
Detailed Physical Characteristics of Lobelia Seeds
Lobelia seeds are consistently among the smallest seeds encountered by gardeners. Their size is often described as microscopic, requiring a magnifying glass for close inspection and making them challenging to handle. A single seed is typically less than half a millimeter in diameter, meaning a small packet can contain thousands of potential plants.
The color generally falls into earthy tones, most commonly light brown, tan, or sometimes reddish-brown. This coloration can vary slightly depending on the specific species. Their shape is not perfectly spherical; instead, they are often slightly irregular, oblong, or angular when viewed under magnification.
The surface texture is not smooth but displays a granular or finely pitted pattern. This texture, combined with their light weight, makes them highly susceptible to dispersal by air currents or water. This minute scale influences the plant’s natural dispersal and the methods required for successful cultivation.
Seed Production and Collection on the Plant
Lobelia seeds develop within tiny, inconspicuous seed capsules that form on the flower stalk after blooming and pollination. These capsules initially remain green while the seeds mature inside. Ripening is indicated by a distinct change in the capsule’s appearance.
Seeds are considered fully mature and ready for collection when the capsule has completely dried out and turned brown or tan. If the capsule is still green, the seeds are not yet viable for storage or sowing. Once dry, the brittle capsule is designed to open easily.
This mechanism allows the plant to naturally disperse its seed, often simply by the wind shaking the stalk. To collect the seeds, a gardener must gently tap or rub the dried capsules over a piece of paper or a fine mesh strainer. Extreme care is necessary, as the minute seeds fall out instantly and are easily lost.
Practical Implications for Sowing
The minuscule size and light-dependent germination of Lobelia seeds dictate specific, careful sowing techniques. Because the seeds are so small, they require light to break dormancy and begin germination. Consequently, they must be surface-sown and should not be covered with soil, only lightly pressed onto the surface to ensure good contact.
Handling these seeds individually is impractical, so a common technique is to mix them with a small amount of fine material, such as horticultural sand or vermiculite. This mixture helps to bulk up the volume, allowing for a more even and controlled distribution over the prepared seed-starting medium.
Watering must be managed carefully to avoid dislodging the seeds from the soil surface. Watering from the bottom, where the tray absorbs water through drainage holes, is the preferred method, as it prevents disturbance. If top watering is necessary, a fine mist setting must be used to keep the soil consistently moist without washing the seeds away.