Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Saxifragales
Family: Crassulaceae
Genus: Aeonium
Species: A. arboreum
Binomial name: Aeonium arboreum
Synonym: Sempervivum arboreum
Common name: Green arboreum, Tree Aeonium, Houseleek tree, Irish rose

Aeonium arboreum is a succulent, subtropical subshrub. It is native to the hillsides of the Canary Islands. It bears rosettes of leaves and large pyramidal panicles of bright yellow flowers in the spring.

The Aeonium species are indiscriminate breeders and just about any species will cross with any other species. "Pure" A. arboreum plants from the wild tend towards having quite thick, almost "meaty" leaves, many of the hybrid plants have a thinner leaf and some are also much narrower as well.

Photo of Aeonium arboreum, possibly hybridized (crossed) with another unknown Aeonium species". 
Aeonium arboreum-003.JPG

Closeup of the flowers.
Aeonium arboreum-001.JPG

A rosette of leaves
Aeonium arboreum-002.JPG 

Thanks to Wikipedia for text and information: