Mexico: Tequila sunrise begins in the heart of the blue agave

Fearsomely spiky plants, fiendishly fiery liquor: Jeremy Atiyah takes a side trip to Jalisco in search of Mexico's national spirit

I am on my way to an important little town in the Mexican state of Jalisco. It's called Tequila. So important is it that one of Mexico's last surviving train services runs here, twice weekly, from Guadalajara. I have chosen to take a bus tour, though, joining an English couple, John and Liz from the West Midlands, and a Mexican family from Oaxaca. We're on the scent of a certain liquor, distilled from the fermented juice of the blue agave plant. Like the town, it is called tequila.

We're driving through a sunny landscape of orchards and forests that looks as fruitful as Tuscany. Trees groan under the weight of avocados, birds of prey float over the Sierra Madre Occidental and snakes (I am sure of it), rustle in the dry grass. We pass into a country devoted to alcohol. Pale blue lines criss-cross the rich, red earth. Jalisco's valleys could be outside St Emilion, except that we are not talking about Cabernet Sauvignon. These are blue agave plants, 100 million of them.

As is often the case in Mexico, Tequila is an oasis of dust surrounded by a sea of fertility. It announces itself with a petrol station and a pile of scrapped cars. But then it's on to the souvenirs, the cobbled streets and the picturesque men in big hats. "If we can't get it through duty-free, shall we drink it here?" says John, pointing at barrels stacked outside shops. "Ooh, yes!" giggles Liz.

The Aztecs had developed a taste for the blue agave's sweet sap long before the conquistadors got here, says our guide. They made sweets from it, for holy purposes, and travelled great distances to collect it. "They also," he says, looking disdainfully at the English tourists, "used its leaves to torture their enemies."

The agave is a wide family of often woody plants, distributed throughout tropical, subtropical, and temperate areas of the world. Most have nasty, lance-shaped, fleshy or toothed leaves sticking up from their bases. The Yucca is one of them, though the house plant's sap is not distilled into liquor. Tequila doesn't come from any old agave, only from the blue agave,Agave tequilana Weber. And by law, it can only be distilled from agave grown in Jalisco, and in bits of four other states. Every tequila must contain at least 51 per cent agave juice (the remainder can be molasses, caramel or yeast).

Sauza, the company providing all this tequilan information, troops us through a plantation of shady fruit trees before a grand ranch house. The sun shines on the bananas and lemons. Our guide, Jose, explains that one man can propagate between 800 and 1,200 baby agave plants per day. The babiesappear around the base of the parent plants; they have to be dug out and replanted in neat rows with plenty of space between.

Thus it is that plantations of blue agave, from a distance, are as pretty as vineyards. But close-up, the plant resembles an explosion of swords projecting from the dry earth. It is not the kind of thing you would wish to encounter if you were wandering lost, at night, in a swimming costume.

And harvesting it is not like plucking apples or grapes either. No matter how much devotion you have lavished on your agave plants, over the requisite eight to 10 years, when it comes to harvesting, the whole plant is annihilated.

Jose begins to dig up a whole agave plant from the sun-baked ground, looking as if he is saving us from a dangerous wild animal. Luckily he has some formidable spades and machetes at his disposal. Then he chops the leaves off the plant, while avoiding the twin hazards of impaling himself on the spines, or cutting his foot off with the machete. Jose offers us the machete to try and the Oaxacan patriarch takes over. "Ladies, stand back," he commands, hacking for dear life.

Once the leaves have been chopped off, the heart of the blue agave, the piña, remains – a football-sized object that resembles a cross between a pineapple and a hand grenade. I can lift one, just. On average, I am told, three litres of tequila can be extracted from just one piña.

Next, we drive to the Sauza distillery. On its wall is a huge mural, in flamboyant Mexican style. I see sun gods, snakes breathing fire, maids in fields, conquistadors, slaves, drunkards, Bacchanalian revellers, nude dancing girls, and mules pulling grindstones and carrying piñas.

Inside, barrels of different sizes and ages are stacked like ingots. "Can't we just drink the stuff?" asks John. No, says a man in a helmet. This kill-joy tells us about the four varieties of tequila. The white, or silver, tequila is not aged, and has nothing added to it. The gold has had colour and caramel added. Thereposado ("rested") tequilas have been kept in casks for two months. The anejo has been stored in oak casks for a year. The straw colouring of some tequilas is often artificial colouring. So which is the best, someone asks? "All of them," interrupts the Oaxacan patriarch, at once. We laugh, thirstily.

To judge by the smart premises, tequila is big business. Sauza is one of the five biggest tequila companies. The Lafitte Rothschild of tequila? "Yes, the company is doing well," says one guide. "But poor Mr Sauza. One of his sons went to Brazil and died, while the other went to New York and became gay. Now he has only his daughter to run the factory for him."

It is time for a drink. We are hit by the sound of machinery and a smell of Christmas pudding, which turns out to be fermenting liquor. We are in the factory. At one end, a pile of agave piñas – at the other, fermenting agave juice. Here, conveyors carry piñas to ovens; there the piñas are crushed and shredded to extract the juice. Eventually, I find myself staring into a 500,000-litre fermentation vat full of syrup-coloured agave-juice, a liquid known as aquamiel, or honey-water.

Finally, we get to the tasting. We drink the liquor neat, with salt and lime only for emergencies. The flavour of some tequilas is similar to that of whiskies and brandies. I buy a bottle of straw-coloured reposado, John and Liz take a selection, and the Oaxacan patriarch settles for a barrel. All return to Guadalajara, profoundly happy.