Blue Agave

Siting: Blue agave is planted at altitudes of roughly 1,500 to 2,000 metres in the volcanic highlands of Jalisco, favoring rich, sandy, fast-draining soil under full sun.

Watering: The crop is grown mostly rainfed, with drip irrigation or rainwater harvesting used in dry spells rather than flood watering, which can rot the base; the plant is frost hardy but stops storing sugar once cold weather sets in.

Propagation: Because flowering is fatal to the plant and its seed is unreliable, growers propagate blue agave from hijuelos, the offsets that sprout at the base, lifting and replanting them; the flower stalk itself is cut from commercial plants so the piña keeps the plant's stored energy.

Commercial blue agave is grown as a single clone, so pathogens that breach one plant's defenses face no resistant neighbor across the field. The complex growers call TMA, tristeza y muerte de agave, combines Fusarium fungi attacking the roots, Erwinia bacteria turning the stem to wet rot, and Thielaviopsis paradoxa following in the damaged tissue, with affected plants yellowing and collapsing at the base before harvest.

Pests: The agave weevil, Scyphophorus acupunctatus, is a recurring pest of the crop, and further rot-causing organisms, including Erwinia carotovora, Enterobacter agglomerans, Pseudomonas mendocina and Serratia species, have been identified in continuing outbreaks.

Monoculture: Continuous planting without rotation drives soil degradation across agave-growing regions, a problem compounded by the crop's near-total lack of genetic diversity.

The piña, or heart of the plant, is cut in its seventh to fourteenth year, depending on growth rate, and typically weighs 40 to 90 kilograms once harvested.

Beverage: The blue agave's core is prized for its high inulin content, which is converted to fermentable sugars by heating the harvested piña; the roasted heart is then pressed to release aguamiel, a sugary liquid that is fermented and distilled into tequila.

Culinary: The processed plant is also made into a syrup used as a sugar substitute for sweetening drinks and in baking.

Blue agave is native to the Mexican states of Jalisco, Colima, Nayarit, Michoacán and Aguascalientes, where it grows wild at higher elevations. In the wild the plant is pollinated by the greater long-nosed bat as well as insects and hummingbirds, producing thousands of seeds, many sterile, before the parent plant dies.

Selected over some four centuries for its fermentable sugar content, cultivated stands are now propagated almost entirely from offsets rather than seed, a shift that has considerably narrowed the crop's genetic diversity.