Sempervivum are a group of succulent perennial plants in the Crassulaceae family. All of the 40 species in this genus have the same basic form and growth habits, although both leaf and flower colors may vary. They are native to many different parts of the world, including Morocco, the Alps, the Balkan Mountains, Iberia, Carpathians, and even parts of the Sahara Desert. Common names for these plants include Houseleeks and Liveforever.
Similar to the cactus, these types of plants store water within their thick leaves. This gives them the ability to survive where many other plants would not, such as stony alpine areas and on top of large rocks. Their short shallow roots quickly soak up any available water which is then transferred to the leaves for storage. The leaves always grow low to the ground in perfect rosette clusters and stay green throughout the winter, even in cold climates.
Most of these plants will produce no flowers for years, if at all. When they do appear, they are very small and star shaped, in white, yellow, pink, green or red. Sempervivum are not grown for their flowers, however, because the ornamental leaves resemble large flowers and may exhibit a variety of colors including bronze, yellow, and dark red. The Hens and Chicks plant is one of the most familiar sempervivum varieties.
All sempervivum spread into large clusters by forming new, tiny rosettes. This makes these plants simple to propagate. A new plant can be obtained by just pulling on of the small rosettes off and planting it in a new location. These small new plants may be watered in but they will survive quite happily without water until it rains. New plants can also be grown easily from seed.
After flowering, the large center leaf rosette will die. Since numerous smaller rosettes have usually grown by this time, the death of the larger plant does not do much harm. The smaller ones will grow and overtake the empty area where the larger one had been. This is the reason why these plants seem to be so long lived.
Sempervivum are hardy in USDA Zones 5 and 6. They may also be grown in colder areas if they are given some type of winter protection. A thick mulch over the garden may be enough since they are low growing and can be completely covered. Potted plants need to be brought indoors in very cold weather or kept in a greenhouse or cold frame to protect them from damaging wind.
Full sun exposure is best for these plants but they will survive in partial shade. Slightly dry gritty soil is preferred since sempervivum plants that are given too much water will grow and spread too quickly. This can make the plants overly weak and may cause them to rot. Too much fertilizer can also cause them to react this way.