While it may look pretty to plant a flowerbed or vegetable garden underneath a tree, it's actually the worst place to put a garden. The roots from flowers, vines and other plants will intermingle with the roots of the tree, and when it comes to water and nutrients, the tree takes priority. Whatever is leftover is given to the other plants. In no time, the garden will wilt and die. Instead, plant shade-loving, low-maintenance ivy and other ground cover under trees.