FOR many years the air around Reggio Calabria carried the odour of gunpowder and death, as mafia clans settled their disagreements the old-fashioned way. These days, the dominant smell is more agreeable. When bergamot trees flower between March and May, the local groves are filled with one of nature’s most overpowering fragrances.

Few tests of olfactory senses are as intense as those in the beauty and fragrance departments of large stores. The overwhelming scent from hundreds of perfumes creates a confusing cocktail for the noses of the many shoppers at this time of year who have to choose between them. Around one-third of annual purchases of perfumes are concentrated in December, to be put in Christmas stockings or placed beneath the Christmas tree. Though their variety seems endless, one thing that many of these gifts have in common is that they contain bergamot oil.

Bergamot puts power into a fine perfume’s top notes, the ingredients that provide the first impression of its scent, explains Sumit Bhasin, the research chief at P&G Prestige, the fragrances division of Procter & Gamble. It also helps diffusion, the way a scent lifts and hangs in the air. P&G Prestige’s famous brands include Dunhill, Gucci and Rochas, and around one half of the perfumes it makes contain bergamot oil. Another perfumer, Gianfranco Ferré, uses it in almost its entire range, which includes a fragrance called Bergamotto Marino.

This natural oil comes from a fruit, Citrus bergamia, a bitter relative of the orange, lemon and lime. Unlike its sweeter counterparts, which are grown around the globe, around 90% of the world’s entire supply of bergamot comes from one small stretch of the Calabrian coast in the tip of Italy’s toe. Indeed, the provincial capital, Reggio Calabria, proudly calls itself the Bergamot City.

According to tradition, bergamot harvesting begins on December 8th, the feast of the Immaculate Conception, but tradition has given way to trade and this year it began in the first week of November. “We need new products. The trend is for perfumes with a fresher, leafier note, and these need oil from fruit picked early,” says Laurent Bert, director of Capua, a family company based near Reggio Calabria. If all goes well, when the harvest ends in mid-March, the region’s 2,300 hectares of bergamot groves will have yielded 24,000 tonnes of fruit, to produce around 120 tonnes of oil. Capua has three-year contracts with some of the 1,500 growers and, having added the production facilities owned by the regional government to its own in 2008, controls around 65% of the market.

The way oil is extracted has been unchanged for 150 years. The fruit is turned against metal points that score the peel which, gently pressed, releases the essence. Then it gets rather more high-tech. Capua’s high-vacuum, low-temperature equipment removes bergaptene, an irritant, from the oil; and it is then stored under nitrogen gas to stop it oxidising. Perfumers like P&G Prestige subject the oil to gas chromatography and other precise forms of measurement to verify its quality before blending it with other fragrances. They could always buy synthetic bergamot, for about a third of the price. But consumers’ strong preference for natural products means that the bergamot groves that line Calabria’s coast are likely to be kept busy for many Christmases to come.