An epiphyte is a plant that grows on another plant, using it for physical support but not stealing nutrients from it.

Picture a tree branch in a rainforest covered with orchids, ferns, and mosses. These plants aren't parasites; they're just using the tree as a platform to reach sunlight. They get their water from rain and their nutrients from dust, debris, and decaying material that collects around their roots. The tree isn't harmed because epiphytes don't tap into its tissues or drain its resources.

Spanish moss, which drapes from trees in the American South, is a familiar epiphyte, though it's not actually a moss at all but a flowering plant related to pineapples. Many stunning orchids are epiphytes, which is why you'll sometimes see them growing in bark chips rather than soil when kept as houseplants.

Epiphytes thrive in tropical rainforests where competition for ground space is fierce and sunlight is scarce at ground level. By growing high in the canopy, they solve both problems at once. Scientists estimate that epiphytes make up nearly half of all plant species in some rainforests, creating entire aerial gardens in the treetops.