In 1981, at the age of 6, Apricot Irving is uprooted to Haiti by her missionary parents. For this child of Southern California, the Caribbean island is enchanting: the green-throated lizards, the mango trees, the sea as warm as bathwater, the music. It is also terrifying, a place where the hospital is so overcrowded that doctors must choose which patients to save, where drought, starvation and military coups weave an endless tapestry of suffering. Nine years later she finds herself striving, with help from Creole songs and upside-down chickens, to convey this teeming, contradictory world to her parents’ church supporters back home. In “The Gospel of Trees,” Ms. Irving, who returned to Haiti in 2010 to cover the earthquake for the radio program “This American Life,” tries again to tell her story of the island.