An air plant is an organism that grows upon or attached to a living plant. Air plants are better known in the scientific world as an epiphyte. Epiphytic plants are sometimes called "air plants" because they do not root in soil. Air plants usually derive only physical support and not nutrition from their host. Unlike parasitic plants air plants rarely damage the host plant.
Air plants use photosynthesis for energy and obtain moisture from the air or from dampness (rain and cloud moisture) on the surface of their hosts. Roots may develop primarily for attachment, and specialized structures (for example, cups and scales) may be used to collect or hold moisture.
Air plants attached to their hosts high in the canopy have an advantage over herbs restricted to the ground where there is less light and herbivores may be more active.
Epiphytic plants are also important to certain animals that may live in their water reservoirs, such as some types of frogs and arthropods.
The best-known epiphytic plants include orchids, bromeliads, and mosses such as Spanish moss of the genus Tillandsia which is a Bromeliad, but epiphytic plants may be found in every major group of the plant kingdom. Assemblages of large epiphytes occur most abundantly in moist tropical forests, but mosses and lichens occur as epiphytes in almost any environment with trees.