San Luís, Cuba (CNN) Looking at the plain, one-story wooden shacks that dot the countryside in Cuba's vuelta abajo region, one would never guess that the farmers here grow one of the island's most valuable natural resources: cigar tobacco.

Though Cuban cigars are famous worldwide, the majority of the tobacco that goes into premium cigars is grown in this relatively small valley in Western Cuba that possesses a unique micro-climate and rich volcanic soil.

The fields behind Hirochi Robaina's house are full of mature tobacco plants, and the drying houses where the tobacco hangs and ages for at least 30 days are stacked to the rafters. But the fifth-generation tobacco grower is still not happy with this year's harvest.

"This year was very complicated because of the weather," he said. "The weather was bad. A lot of rain and wind."

Usually, the winter months are the dry season, perfect for growing and harvesting tobacco for top brands like Cohiba, Montecristo and Partagas.

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