Blue agave is the common name given to the cultivated species of agave, Agave tequilana Weber var. azul used in the production of tequila and blue agave nectar. It's one of 136 species native to Mexico, and the wild version of this succulent thrives in Jalisco, where it is nourished by volcanic soils and pollinated by long-nosed bats. A mature plant can grow to be 5 to 8 feet tall, and 7 to 12 feet wide. Like most agaves, it has a large rosette of thick fleshy leaves, lined with teeth, and ending in a sharp point. The central core of the blue agave, known as a piña (because the swollen stem of the plant resembles a pineapple, once the leaves are removed), is juiced to get the liquid that will be filtered (for nectar) or fermented (for tequila). The blue agave is commercially harvested after about 12 years, when the heart of the plant reaches about 80 lbs (in the highlands, plants can
produce piñas weighing hundreds of pounds). A 100 lb. core will
eventually produce about 6 liters of tequila.
Blue agave can reproduce sexually or non-sexually, via runners. In order to increase their harvest, farmers don't let the plants reach sexual maturity. Once a plant produces an inflorescense, known as the quiote, it is severed, so that the plant puts its energy into swelling the piña, not producing flowers and seeds (Sorry, bats). Farmers sever the runners ("hijuelos") for new plantings, but as these cuttings are genetically identical to the mother plant, the tequila industry relies on a genetic monoculture, vulnerable to fungus and disease.
Sources:
“Blue Agave Nectar.” <http://www.blueagavenectar.com/agavenectarmanufacturer.html> (September 3, 2008)
Hector T. Arita and Don E. Wilson. “Long-Nosed Bats and Agaves: The Tequila Connection.” BATS Magazine, Vol. 4, No. 5. December 1987. <http://www.batcon.org/batsmag/v5n4-4.html> (September 3, 2008)
Ian Chadwick. “Agave: More than just tequila.” In Search of the Blue Agave: Tequila and the Heart of Mexico. June 27, 2007. <http://www.ianchadwick.com/tequila/agave.htm> (September 3, 2008)
---. “Tequila Production: From Raw Agave to Epicurean Elixir.” In Search of the Blue Agave: Tequila and the Heart of Mexico. June 27, 2007. <http://www.ianchadwick.com/tequila/production.htm> (September 3, 2008)
Domingo Ruvalcaba-Ruiz and Benjamin Rodríguez-Garay. “Aberrant meiotic behavior in Agave tequilana Weber var. azul.” BMC Plant Biology 2002, 2:10 doi:10.1186/1471-2229-2-10 <http://www.biomedcentral.com/1471-2229/2/10> (September 3, 2008)