agave

agave, (genus Agave), genus of the some 200 species of the family Asparagaceae (formerly Agavaceae), native to arid and semiarid regions of the Americas, particularly Mexico, and the Caribbean. The genus contains a number of economically important species, especially those required for the production of mescal liquors, including the blue agave (Agave tequilana) used for tequila. Sisal (A. sisalana), henequen (A. fourcroydes), and cantala (A. cantala) are significant sources of fibre and are of interest as potential bioenergy crops. The century plant, or maguey (A. americana), and blue agave are the primary sources of agave nectar, a syrupy sweetener. Additionally, a number of species are grown as ornamentals in desert landscaping.

Agaves are characterized by a rosette of succulent or leathery leaves that range in size from a few centimetres to more than 2.5 metres (8 feet) in length, depending on the species. Most bear spines along the edges and the tip of the leaf, for which they are occasionally confused with unrelated cacti. The leaves range in colour from pale green to blue-grey and can be variegated or striped. Many species are able to reproduce vegetatively and generate clonal rosettes at the base of the main stem or nearby via underground rhizomes; some species produce bulbils (bulblike structures that can form new plants) on the inflorescence. The plants are generally monocarpic—meaning that each rosette dies after flowering and fruiting—and most do not live longer than 30 years. The yellow, pale green, or red flowers are borne in tall branching or unbranching inflorescences that can reach more than 9 metres (30 feet) in height in some species. Each flower consists of six petals and an inferior ovary (i.e., the other flower parts are attached above the ovary) and produces copious amounts of nectar. The flowers are pollinated by bats, insects such as bees and hawk moths, or birds, depending on the species. The flowers produce capsule fruits. As an adaptation to their arid habitats, agaves use a photosynthetic pathway known as crassulacean acid metabolism (CAM), in which carbon dioxide is fixed at night to limit the amount of water lost from the leaf stomata.

Agave plants have a long history of ethnobotanical importance, especially to the peoples of Mexico, where the genus is most diverse. Many species have strong fibrous tissue in their leaves, which makes them useful for ropes, brushes, sandals, nets, sleeping mats, and other similar items. The fibres of some species can be removed with the terminal spine of the leaf still attached, forming a type of needle and thread. In many species, the leaves of the rosette can be removed to reveal the thick stem, or “heart,” which can be roasted and eaten directly or ground into edible patties. The stem is particularly dense in carbohydrates immediately before flowering, and it is also the source of mescal alcohols and agave nectar. To prepare mescal, the sap of roasted or pressure-cooked agave hearts is fermented and distilled; different species are used for different types of mescal, with blue agave being the only species used for tequila. Similarly, agave nectar, a syrupy sweetener used as a sugar alternative, is not true floral nectar and is made by extracting, filtering, and heating the sap of the hearts of several species, notably blue agave and the century plant. Pulque, another traditional Mexican alcohol, is made by fermenting the sap of the inflorescence stalk. The raw sap of most Agave species is considered toxic and requires cooking prior to ingestion.