The Sempervivum, or "houseleek" or "hens and chicks," is a hardy alpine succulent that was naturalized in the United Kingdom. Sempervivums prefer to grow in drier conditions and enjoy the cold. They are hardy to minus 25 degrees F and are not sensitive to heavy frosts or freezing. With star-shaped, exotic-looking flowers and fruits, there are about 50 different species of Sempervivums and more than 3,000 cultivars. These species display a wide range of rosette colors and sizes. In a sunny, dry spot, Sempervivums will blossom and propagate on their own by growing offsets with very little care.
Plant the Sempervivums during springtime in a rock garden, planter, trough or even between bricks or stones in walls. Position the Sempervivums in full sunlight and keep them only slightly moist to dry.
Plant the Sempervivums in shallow, gritty, free-draining compost mixed with 25 to 50 percent sharp sand and grit. Place the Sempervivum's root system into the compost mixture. Apply a top dressing of grit between the Sempervivums.
Remove rosettes carefully after they die. The rosettes will bloom only once and then die, but most Sempervivum species and cultivars produce many offsets that fill in the space after a rosette is removed. After removing the rosette, fill in the hole with gritty compost.
Protect the Sempervivums from winter rains, especially if you're planting the hairy Sempervivum cultivars such as Jovibarba or Rosularia. Suspend a small pane of glass over the plants or place the top half of a clear plastic bottle over the Sempervivums. Another alternative is to gently unearth the plants and pot them for over-winter storage indoors or a cool greenhouse.
Propagate Sempervivums by removing the offsets when their roots begin to develop. Grow the offsets separately from the parent plant to create a new Sempervivum plant. Offsets grow from the base of a rosette, connected by a long stolon, which eventually withers after the offset develops its own roots and anchors next to the parent plant. Cut off the stolon just below the base of the offset to boost root growth from the rosette's base.