Aeonium, the tree houseleeks, 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 αἰώνιος / aiōnios (ageless).[1] While most of them are native to the Canary Islands, some are found in Madeira, Cape Verde, Morocco, in East Africa (Ethiopia, Somalia, Uganda, Tanzania and Kenya) and Yemen.
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 and A. valverdense. 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.
All but two species are native to at least one of three different Macaronesian archipelagos (the Canary Islands, Madeira, or Cape Verde) Most aeoniums are from the Canary Islands,[2] [3] The only species not native to these three Macaronesian island groups (Aeonium stuessyi and Aeonium leucoblepharum) are found in Ethiopia, Kenya and Tanzania; and Ethiopia, Kenya, Sudan, Uganda and Yemen, respectively. Aeonium arboreum is native to both the Canary Islands and Morocco.
Species accepted by Plants of the World Online as of April 2023:[4]
| Aeonium aizoon (Bolle) T.H.M.Mes | Canary Islands (Tenerife) | ||
| Aeonium appendiculatum Bañares | Canary Islands (La Gomera) | ||
| Aeonium arboreum (L.) Webb & Berthel. | Canary Islands (Gran Canaria, Tenerife, La Gomera, La Palma, El Hierro);Morocco | ||
| Aeonium aureum (C.Sm. ex Hornem.) T.H.M.Mes | Canary Islands (Gran Canaria, Tenerife) | ||
| Aeonium balsamiferum Webb & Berthel. | Canary Islands (Lanzarote, Fuerteventura) | ||
| Aeonium canariense (L.) Webb & Berthel. | Canary Islands (Gran Canaria, Tenerife; La Gomera, La Palma, El Hierro) | ||
| Aeonium castello-paivae Bolle | Canary Islands (La Gomera) | ||
| Aeonium ciliatum (Willd.) Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium cuneatum Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium davidbramwelii H.Y.Liu | Canary Islands (La Palma) | ||
| Aeonium decorum Webb ex Bolle | Canary Islands (Tenerife, La Gomera) | ||
| Aeonium dodrantale (Willd.) T.H.M.Mes | Canary Islands (Tenerife) | ||
| Aeonium glandulosum (Aiton) Webb & Berthel. | Maderia (Madeira, Desertas, Porto Santo) | ||
| Aeonium glutinosum (Aiton) Webb & Berthel. | Madeira (Madeira, Desertas) | ||
| Aeonium gomerense (Praeger) Praeger | Canary Islands (La Gomera) | ||
| Aeonium goochiae (Christ.) Praeger | Canary Islands (La Palma) | ||
| Aeonium gorgoneum J. A. Schmidt | Cabo Verde (Santo Antão, São Nicolau, São Vicente) | ||
| Aeonium haworthii (Salm-Dyck ex Webb & Berthel.) Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium hierrense (R. P. Murray) Pit. & Proust. | Canary Islands (La Palma, El Hierro) | ||
| Aeonium lancerottense (Praeger) Praeger | Canary Islands (Lanzarote) | ||
| Aeonium leucoblepharum Webb ex A. Richard | Yemen, Ethiopia, Sudan, Kenya, Uganda | ||
| Aeonium lindleyi Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium liui Arango | Canary Islands (Tenerife) | ||
| Aeonium nobile (Praeger) Praeger | Canary Islands (La Palma) | ||
| Aeonium percarneum (R. P. Murray) Pit. & Proust. | Canary Islands (Gran Canaria) | ||
| Aeonium rubrolineatum Svent. | Canary Islands (La Gomera) | ||
| Aeonium saundersii Bolle | Canary Islands (La Gomera) | ||
| Aeonium sedifolium (Webb ex Bolle) Pit. & Proust. | Canary Islands (Tenerife, La Gomera, La Palma)) | ||
| Aeonium simsii (Sweet) Stearn. | Canary Islands (Gran Canaria) | ||
| Aeonium smithii (Sims) Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium spathulatum (Hornem.) Praeger | Canary Islands (Gran Canaria, Tenerife; La Gomera, La Palma, El Hierro) | ||
| Aeonium stuessyi H.-Y. Liu | Ethiopia, Kenya, Tanzania | ||
| Aeonium tabuliforme (Haw.) Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium undulatum Webb & Berthel. | Canary Islands (Gran Canaria) | ||
| Aeonium urbicum (C. Sm. ex Hornem.) Webb & Berthel. | Canary Islands (Tenerife) | ||
| Aeonium valverdense (Praeger) Praeger | Canary Islands (El Hierro) |
Much hybridising has been done, resulting in several cultivars of mixed or unknown parentage. The following species and cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-
Hybridising between Aeonium species or cultivars and other Crassulaeceae species or cultivars has produced intergeneric crosses:
Some species have been introduced in California.[13]
UK national collections of aeoniums are held by Mellie Lewis at Clun in Shropshire[14] and by Inverewe at Poolewe, Wester Ross in Scotland.[15]