Sempervivum - Identification

Identification

The genus Sempervivum is easy to recognize, but its species are often not easy to identify. Even one single clone can look very different under various growth conditions (modifications) or different times of the year. The members of this genus are very similar and closely linked to each other. As a consequence, many subspecies, varieties, and forms were described, without well-defined limits between them. As a second consequence, there are a high frequency of natural hybrids in this genus and the possibility of back-crossings of these. However, more or less 40 species can be individualized in the whole area of the genus, but there are many more local populations, without nomenclatural valour but with sometimes their own characters.

In the Alps, for example, the most distributed species are Sempervivum tectorum (Common Houseleek, sometimes called Sempervivum alpinum), Sempervivum montanum (Mountain Houseleek) and Sempervivum arachnoideum (Cobwebbed Houseleek), each one with several subspecies. More local are the yellow-flowered S. wulfenii and S. grandiflorum, and the beautiful Limestone Houseleek (S. calcareum). More rare are S. dolomiticum and mainly S. pittonii. S. pittonii is a small yellow-flowered jewel which grows only on two mountains slopes near Kraubath in the Mur valley in Austria and is very threatened.

On roofs or old walls S. tectorum can be found, more or less wild, very far out of its natural area. It is a very old medicinal and witch-plant. Some superstitious people believe that this plant is able to protect a house from lightning.