Aeonium (tree houseleek) is a genus of about 35 species of succulent, subtropical plants of the family Crassulaceae. Many species are popular in horticulture. The genus name comes from the ancient Greek "aionos" (ageless). While most of them are native to the Canary Islands, some are found in Madeira, Morocco, and in East Africa (for example in the Semien Mountains of Ethiopia). The succulent leaves are typically arranged on a basal stem, in a dense, spreading rosette. A feature which distinguishes this genus from many of its relatives is the manner in which the flowers bear free petals, and are divided into 6 or 12 sections. Each rosette produces a central inflorescence only once, and then dies back (though it will usually branch or offset to produce ensuing rosettes). Low-growing Aeonium species are A. tabuliforme and A. smithii; large species include A. arboreum, A. valverdense and A. holochrysum. They are related to the genera Sempervivum, Aichryson and Monanthes, as can be seen by their similar flower and inflorescences. Recently, the genus Greenovia has been placed within Aeonium.