Sweet William (Dianthus barbatus) is a popular garden favorite, often grown as a biennial or short-lived perennial, known for its dense clusters of vibrant, fragrant flowers. These plants bloom in a wide variety of colors, ranging from white to deep crimson, and readily produce seeds. Understanding the characteristics of these seeds is essential for successful propagation and identification.
Visual Identification of Sweet William Seeds
Sweet William seeds are noticeably small, typically measuring less than two millimeters across, appearing like tiny, flat kernels. They exhibit a deep blackish-brown coloration. Their shape is irregular, often described as slightly triangular or shield-like, rather than perfectly round or oval.
The seed coat texture is generally rough or finely textured. This combination of diminutive size, dark color, and unusual shape distinguishes them from the seeds of many other common garden flowers.
Collecting Seeds from Mature Plants
The seeds are contained within a small, dry fruit called a capsule, which develops after the flowers have faded. This capsule is located at the center of the spent flower head, surrounded by a dried calyx. Seeds are ready for collection when the entire flower head and the capsule turn a uniform brown and become brittle.
The dry capsule is dehiscent, meaning it naturally splits open at the top with four small teeth to release the seeds. The best time to harvest is usually in the late summer or early fall, once the capsules are fully dry but before they scatter their contents. Tipping the spent flower head into a paper bag is an easy way to collect the loose seeds.
Sowing and Germination Basics
Sweet William seeds can be sown directly into the garden in the fall or early spring, or started indoors for an earlier display. Because the seeds are small, they require light for successful germination and must not be buried deeply. A very light covering of soil, or simply pressing them onto the soil surface, is sufficient.
Optimal germination occurs at soil temperatures between 18 and 22 degrees Celsius (65–72°F), with seedlings typically emerging within seven to fourteen days. When starting indoors, sow the seeds approximately six to eight weeks before the last expected frost date. Providing consistent, light moisture is important during this initial germination period.