Pachyphytum is a small genus of leaf succulents in the stonecrop family, Crassulaceae, native to eastern and central Mexico. The genus was established in 1841 by Heinrich Friedrich Link, Johann Friedrich Klotzsch and Christoph Friedrich Otto, who published the first description in the German horticultural journal Allgemeine Gartenzeitung. The name combines the ancient Greek pachys ("thick") and phyton ("plant"), a direct reference to the swollen, water-storing leaves that define the group.
Plants form hairless rosettes carried on slender stems. When young the stems may stand upright to around 70 cm, but with age they become prostrate and can exceed a metre in length, often hanging or sprawling over the rocky surfaces they grow on. Each rosette is typically 6–20 cm across and made up of roughly ten thick, fleshy leaves. The foliage is one of the genus's most distinctive features: many species carry a dense, waxy bloom that gives the leaves an intensely blue, teal or lavender-frosted appearance, and in the best-known species, Pachyphytum oviferum, the egg-shaped leaves look uncannily like sugared almonds.
In the wild Pachyphytum is restricted to a relatively narrow range in eastern and central Mexico, where the plants colonise rocky, well-drained slopes between about 600 and 2500 metres elevation. A handful of species, notably P. oviferum and P. hookeri, have been carried in cultivation to other parts of Latin America and now occur, naturalised or escaped, in countries such as Brazil, Costa Rica, Ecuador, Peru and Bolivia.
Taxonomically the genus sits in the tribe Sedeae and is closely allied to other New World stonecrops; Diotostemon Salm-Dyck is treated as a synonym, and the genus is divided into two sections (Diotostemon and Pachyphytum), with roughly 25 recognised species. Pachyphytum oviferum, the moonstone or sugaralmond plant, is by far the most familiar member, but P. hookeri, P. bracteosum, P. compactum and P. longifolium are also widely grown.
Etymology
The genus name Pachyphytum was coined from the ancient Greek roots pachys, meaning "thick", and phyton, meaning "plant". The name is a direct reference to the succulent, water-storing nature of the leaves, which are notably plump and fleshy across all members of the genus.
Distribution
Pachyphytum is naturally restricted to eastern and central Mexico, where it occurs on rocky, well-drained slopes between about 600 and 2500 metres elevation. Outside this native range, several species — most prominently P. oviferum and P. hookeri — have escaped cultivation and become established in parts of Latin America, with records from Brazil, Costa Rica, Ecuador, Peru and Bolivia.
Ecology
In their Mexican range, Pachyphytum species grow as rosette-forming leaf succulents on rocky, well-drained mountain slopes between 600 and 2500 metres. The thick, waxy leaves are an adaptation to these exposed, sun-baked sites, storing water and reflecting strong light through their characteristic blue or lavender bloom.
Taxonomy
Pachyphytum was described in 1841 by Heinrich Friedrich Link, Johann Friedrich Klotzsch and Christoph Friedrich Otto in the German journal Allgemeine Gartenzeitung (volume 9, page 9). It is placed in the family Crassulaceae, order Saxifragales, within the tribe Sedeae. Diotostemon Salm-Dyck is treated as a synonym of Pachyphytum, and the genus is divided into two sections — Diotostemon and Pachyphytum — with about 25 recognised species; GBIF lists 28 descendant taxa under the accepted genus name.
History
The genus was first published in 1841 in the German horticultural periodical Allgemeine Gartenzeitung ("General Gardening Newspaper"), in a joint description by the botanists Heinrich Friedrich Link, Johann Friedrich Klotzsch and Christoph Friedrich Otto.
