Houseleek (sempervivum, Linn.), a genus of plants of the natural order crassulacece, having thick succulent stems and leaves, the former frequently short, with the leaves so closely crowded upon them as to form a dense rosette, and ornamental flowers, either yellow or red. The houseleeks are found in the mountains of southern and central Europe, the Canaries, and various parts of Asia and Africa. The common houseleek (S. tectorum, Linn.) has very thick, succulent leaves, disposed about a short stem in a circular manner. It will grow in the most scanty soils and where it is exposed to drought, patches of it several feet in circumference thriving for years upon the exposed surfaces of rocks that are partially shaded. In Europe it is very common upon the thatched roofs of houses; it was formerly supposed to serve as a protection from lightning, and in early times every house was required to have it; the custom still prevails, and it is said that the plant tends to preserve the thatch. Within a few years the taste in gardening has led to the use of sempervivums and other succulents for forming beds of a mosaic of living plants.
The neat compact habit of the houseleeks and the related cotyledons, echeverias, etc, as well as the variety in color presented by the leaves, especially adapt them to this purpose; and these plants, which were formerly kept as single specimens by the curious, are now raised by the florists in large quantities for ornamental planting. One of the most valued for this purpose is S. calcareum from the Alps (incorrectly 8. Galifornicum of florists), and several others are employed. A very striking and interesting little species is the cobweb houseleek (S. arachnoideum), also an alpine species; its rosettes, about an inch across, grow close together in large clumps; the tiny leaves are connected by a fine down which passes from tip to tip, making the plant look as if an industrious spider had spun its web over it. Where sparrows abound the plant cannot be grown in perfection, as these birds rob it of the web to use in their nests. The tree houseleek (S. arboreum), from the Canaries, has a branching stem 3 ft. or more high, each branch terminated by a handsome rosette of green leaves, or in the varieties yellow margined or purple. It is a greenhouse plant, and was formerly common as a window plant. - The houseleeks are not remarkable for useful qualities.
The fresh leaves of the ensao of Madeira (S. glutinosum, Aiton) are used by the fishermen to rub upon their nets, to preserve them. Malic acid combined with lime exists in S. tectorum. Its juices are considered cooling, and its bruised leaves are used in domestic practice as applications to burns, ulcers, and inflammation, and from them also a simple and cooling salve is prepared.
Common Houseleek (Sempervivum tectorum).
Cobweb Houseleek (Sempervivum arachnoideum).
Tree Houseleek (Sempervivum arboreum).