Verdant describes land that is covered in fresh, living green — grass, leaves, young crops. It is not just the colour green; it carries the feeling that things are growing well, that there has been rain, that the place is alive. A verdant valley, verdant hills, a verdant lawn after spring. This is a written, literary word. Travel writing loves it, poetry loves it, estate agents love it. Nobody looks out of a car window and says "wow, verdant." They say "so green!" So when you use it, you are choosing a slightly grand, admiring tone on purpose. It describes places and plant-covered surfaces, not objects — a verdant hillside, yes; a verdant shirt, no. There is a second, much rarer use meaning inexperienced or naive, the same way English uses "green" for a beginner, but you will almost never meet it, and it would sound strange in ordinary writing today.