On a rooftop farm in Brooklyn one sunny afternoon, dozens of tomato plants heavy with fruit swayed in the wind, a farmer stooped over rows of dandelion greens and the customers kept coming. They climbed through the door to the 65,000-sq.-foot roof of the Brooklyn Grange Farm, in the city’s navy yards, across the water from Manhattan, and without fail they exclaimed with delight. “I love it. This is beautiful!” said Giovanni Cipolla, a grey-haired man who bought a bunch of dandelion and remarked that the only other place he could buy greens this fresh was Italy.