Sempervivum 'Onyx'

Sempervivum 'Onyx' is an impressive large-rosetted succulent from the SuperSemps® series, selected for its exceptional size, strong architectural form and extraordinarily dark foliage. Its broad, pointed leaves develop rich shades of royal purple, burgundy and deep mahogany-black, creating one of the darkest displays among the Sempervivums we grow.

Dark Mahogany-Black Colour

The outstanding feature of 'Onyx' is its remarkably deep pigmentation. The substantial leaves form a bold, symmetrical rosette with colours ranging from dark burgundy and purple through to mahogany-black. Under favourable growing conditions the centre can become particularly dark, giving the rosette the dramatic, almost black appearance that inspired its gemstone name.

As with other Sempervivums, colour will vary with season and growing conditions. Light intensity, temperature, moisture and active growth can all influence the balance between greener, burgundy and darker purple tones. 'Onyx', however, has been specifically selected for its ability to maintain exceptionally dark colouring and can provide impressive colour throughout much of the year.

Exceptionally Large Rosettes

'Onyx' is notable not only for its colour but also for its size. Mature rosettes can reach approximately 20 cm across under suitable conditions, considerably larger than many traditional Sempervivum cultivars. The thick, pointed leaves form a striking geometric rosette that becomes increasingly impressive as the plant matures.

Offsets develop around the parent plant to form an expanding colony of smaller rosettes. These can be left attached for a naturally clustered display or separated once established to produce additional plants. Its combination of substantial size and near-black foliage makes 'Onyx' particularly effective as a specimen plant in decorative pots, rockeries and mixed succulent displays.

Flowers & the Sempervivum Life Cycle

Mature Sempervivum rosettes may eventually produce an upright leafy flower stem carrying clusters of star-shaped pink flowers. These flowers are attractive to bees and other beneficial pollinating insects.

Each individual rosette is monocarpic, meaning it flowers once and then gradually dies. By this stage the plant will generally have produced offsets around it, which continue growing and maintain the colony. Once flowering has finished, the spent flower stem and declining rosette can simply be removed.

Growing Sempervivum 'Onyx'

'Onyx' performs best outdoors in a bright position with excellent drainage. Plenty of sunlight encourages strong, compact growth and helps maintain its characteristic dark pigmentation. It is also notably tolerant of sunny conditions and, once established, requires relatively little water.

Grow in a gritty, free-draining succulent mix and water thoroughly when required, allowing the growing medium to dry between waterings. Avoid continually wet soil, particularly during cooler weather. Like other Sempervivums, 'Onyx' is remarkably cold and frost tolerant when grown in well-drained conditions.

In very hot Australian locations, plants grown in small containers may benefit from some protection from extreme afternoon summer heat. Good airflow and drainage are particularly important during periods of hot or wet weather.

A Standout SuperSemps® Cultivar

Developed as part of the SuperSemps® series of unusually large Sempervivums, 'Onyx' combines the toughness and easy-care character of hens and chicks with rosettes approaching the scale normally associated with much larger succulents. Its impressive size, geometric form and dark mahogany-black colouring make it an excellent choice for collectors looking for something genuinely distinctive.

Sempervivum 'Onyx' plants for sale shown in 70mm pot. You will receive same or similar plants as those shown in images. Colours will vary depending on time of year and growing conditions.