Epiphytic orchids grow on structures such as trees
. Although they grow on the tree, they can not feed on the tree. They cling by their roots fleshy branches or bark of trees. Organic substances that accumulate in the roots and branches are used as a nutrient for plants. The roots of epiphytic orchids may also maintain the plant during wet periods and dry. The tough, fibrous core of the root is surrounded by a spongy-white envelope that can absorb water easily. When it rains, this cover absorbs moisture. When fully saturated, it becomes bright green. The roots of orchids to retain moisture and gradually release to the plant tissue. There are also some species of epiphytic orchids that cling to rocks. When they are hung on trees or rocks, epiphytes grow in filtered light and always in an open, airy situation.