Crouching among the pink carnations, 12-year-old Luis ties knots in a 30-foot nylon line that keeps the stems upright at the Senda Brava farm near the Bogota suburb of Madrid. He has been busy since dawn and will continue until 10 p.m., working overtime to hit export quotas. His nine-year-old brother, Manuel, is watering the flowers. Inside the greenhouse the stench of sprayed pesticides makes the youngsters dizzy, but they have no time to rest. Summer is peak season in Colombia for harvesting the flowers that are farmed around Bogota, Cali, and Medellin.

Cut flowers are Colombia's new miracle export, hailed as an alternative to cocaine. Britain, for example, buys almost $50 million worth of carnations alone from Colombia each year. Colombia also exports roses, lilies, and other flowers.

But the hidden cost of this trade is high for the children who provide the growers with cheap labor and for the workers exposed to pesticides, some of which are banned in Europe and the United States. The farms "like to employ children because we have small hands and can work fast," says Luis. [His name and that of all the other workers have been changed.] "When they spray the pesticides, I get sick, but my family needs the money."

Although the minimum wage in Colombia is now fixed at 118,000 pesos ($132) a month, Luis is paid only 60,000 pesos. Manuel receives 1, 000 pesos per flower bed. By law, children from 12 to 14 may work a maximum of only four hours a day, for the same pay as an adult. But as in other areas, the law in Colombia is often a theory, not a practice.

There are no official figures for the number of children working on flower farms. Colombia's Ministry of Labor vehemently denies that children are working illegally there. The Observer, though, found ample evidence of the hundreds of tiny pairs of hands employed behind locked gates. Every morning youngsters from the barrios of Bogota- -suburbs such as Funza, Madrid, and Mosquera--are collected by bus and taken to the farms. In Bogota itself, a city of 6 million, the alternatives are grim. Five-year-olds sniffing glue sit dazed under a bridge where pimps trawl for child prostitutes. Arturio, 11, Julio, 13, and Giovanni, 15, were all living on the streets until they found work on flower farms. They say they are thrilled to be employed, but they do not realize the consequences of breathing insecticides.

"It is a time bomb," says Dr. Gabriel Rueda, who is working with Cactus, an independent social-welfare group in Bogota. "When they are eight or nine, we see children mixing pesticides in the tanks without gloves, masks, or any protection. We may not see the effects until five to 20 years later when they can no longer move their hands. Many farms use very dangerous organochlorides, which are prohibited in many countries. " He says these toxins can cause miscarriage, mutations of the fetus, disruption of the central nervous system leading to paralysis or epilepsy, and cancer.

Tanya, 15, can no longer work. Since the age of 13, she says, she has been digging flower beds, weeding, pruning, and cutting up to 1,000 stems a day on the Santa Cruz farm in Madrid. "I get dizzy and faint. My stomach hurts. Sometimes I feel as if I'm drunk: My vision goes and I can't stand up," she says. Tanya is not receiving sick pay or medical care because she was employed, like most workers, on temporary contracts, which do not include benefits.

For nine years, Marianne, now 34, was one of the 70,000 women workers in the industry. "Then I started vomiting and losing my vision and had to stop." Her two sons, 13 and 15, both work in the flower trade. She says, "Of course I am worried for the boys' health, and they can't go to school because they have no time, but what can I do?"

In the hospital at Madrid, where 90 percent of the patients work in the flower industry, Dr. Oswald Garcia says he is afraid of being fired if he speaks out about the high rate of miscarriage, respiratory problems, leukemia, and loss of limb control he sees among flower workers. Rueda explains: "His boss has already publicly stated that these endemic problems are caused by the dust of the savannah, not toxic poisoning."

In 1994, the Colombian Ministry of Health banned seven organochloride pesticides, including lindane and endo-sullen. But workers say these pesticides are still used illegally on some farms. Scientists agree that there is no proven link between many insecticides and fatal human diseases. However, malnutrition, which is also endemic to slum life, is known to aggravate the harmful effects of pesticides.

With new markets opening up in Russia and Japan, Colombian flower growers are worried about their international image. Isabel Patino, president of the Association of Colombian Flower Growers, encourages visits to showcase farms. But she admits that not all farms are law-abiding and says the problems of child labor and pesticide usage are alarming.

David Knight, manager of Interflora Flowers in Britain, says, "The Colombian government has good intentions, but it's a question of mechanics. We are aware that conditions are awful in some farms and good in others."

At one of the many farms where visitors are not welcome--Santa Cruz farm--armed guards man the gates, and barbed wire rings the perimeter. Inside, children are working on the flowers. Many are too terrified of reprisals to talk, but some speak out bravely about the conditions- -such as Mercedes Sosa, 15, who says: "In your country, flowers are a symbol of love. Here they are a symbol of suffering."