Mr. Flower Fantastic — it’s his nom de bloom — spoke with me last week in the garden’s Enid A. Haupt Conservatory, a steamy, sunny refuge from the Bronx’s surrounding Arctic air. He and a team were installing “The Orchid Show: Mr. Flower Fantastic’s Concrete Jungle,” an urban landscape overrun by wild delights. Opening on Saturday and running through April 26, the exhibition reflects the two Jamaicas that have influenced its designer: Jamaica, Queens, where he grew up, and Jamaica, the island, his mother’s ancestral home.