The genus Sempervivum, commonly known as Hens and Chicks, is a popular group of hardy, drought-tolerant succulents known for their dense, rosette-shaped foliage. Gardeners usually propagate these plants by separating the small offsets, or “chicks,” from the larger parent rosette, the “hen.” While vegetative propagation is the simplest method, growing new plants from seed allows for genetic variation and the development of unique varieties. This process requires recognizing the appearance of the minute seeds.
Identifying Sempervivum Seeds
Sempervivum seeds are notable for their extremely minute size, often described as dust-like or akin to fine sand. They are significantly smaller than most common garden seeds, making them challenging to handle.
Each seed is typically irregular in shape and lacks a uniform, smooth surface. Their coloration ranges from light tan or beige to a reddish-brown hue. Due to their small size, they require careful handling to prevent them from being lost to a breeze or misplacing them on the planting medium. This characteristic necessitates specific surface-sowing techniques rather than deep planting.
How and When Seeds Develop
Seed production begins when a mature Sempervivum rosette enters its final life stage. The mother rosette is monocarpic, meaning it flowers once and dies after producing seeds. The rosette grows a tall, thick flower stalk, up to 12 inches in height, emerging from its center. This stalk supports a cluster of small, star-shaped flowers, often pink, red, or yellow, which appear during the summer months.
After pollination, the flower stalk dries and withers. The plant directs energy toward forming small, dry seed capsules on the spent stalk. These capsules should be left on the plant to fully mature and turn brown before harvesting. The best time for collecting viable seeds is typically in the late summer or early fall when the capsules are completely dry and brittle. Seeds are then extracted by gently crushing the dried seed heads over a container.
Starting New Plants From Seeds
Propagating Sempervivum from seed is a slow process, but it generates new genetic combinations. Successful germination requires a sterile, well-draining medium, such as a mix of potting soil and grit or perlite, to prevent rot in the delicate seedlings. The minute seeds must be sown on the surface of the soil and should not be covered, as they require light to initiate germination.
A consistent temperature of around 70°F (21°C) is ideal for sprouting. If germination does not occur within a month, some varieties may benefit from cold stratification, which involves placing the moistened seeds in a refrigerator for two to four weeks. After germination, which can take several weeks, the tiny seedlings must be kept lightly moist and gradually introduced to brighter light. The resulting seedlings take a long time to reach mature rosette size.