Cocaine is probably the last thing most people think about when buying roses. 

But every year, police and growers in Colombia must work around the clock to make sure that the romance of Valentine's Day isn't spoiled by the drug, the nation's other major export along with flowers. 

As much as 150 metric tonnes of flowers leave Colombia on 30-plus jumbo cargo planes daily starting in late January, presenting an opportunity for the country's ingenious drug cartels to penetrate the frenzied, overworked chain of suppliers and stash drugs amid the roses. 

"Without a doubt we're a target," said Augusto Solano, president of the Colombian flower exporters' association. 

Security protocols that the flower industry developed with police begin the moment that refrigerated trucks carrying rose buds depart dozens of flower farms dotting the waterlogged savannah surrounding Colombia's capital. Once the flowers are inside the airport, 100 police offices equipped with 15 drug-sniffing dogs and electronic scanners inspect each shipment. 

Last year, police said they found almost 90kgs of cocaine hidden in flower boxes. 

"We have to guarantee that our flower exports aren't contaminated by criminal gangs," Col. Julio Triana said as he and his drug-sniffing Labrador retriever walked through the refrigerated warehouse where flowers are kept before being loaded onto cargo planes. 

Colombia's flower industry took off in the early 1990s when the US Congress passed a law eliminating tariffs on goods from Andean drug-producing nations in a bid to encourage legal exports. That Colombia's criminals now train their eyes on flower shipments as a way to smuggle drugs into the U.S. is a sign of just how much the industry has blossomed. It is now is the world's second-largest cut flower exporter, after the Netherlands, and the top supplier to the US. 

The season before Valentine's Day is the busiest time of the year for Colombia's growers, when the 130,000 people employed at hundreds of flower farms work nonstop to ship some 500 million stems, mostly to the United States but other parts of the world as well.