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| Ball moss is a common epiphyte & is typical of what most people imagine when they think "air plant." It attaches itself to a tree & spends its life there. |
Epiphyte derives from Greek epi- 'upon' and phyton 'plant'. An epiphyte is a non-parasitic, organism that grows on a plant and that derives moisture & nutrition from its surrounding ecosystem. Most people associate this with the terrestrial epiphytes or "air plants" that make their living without touching the ground, but wait, there's more...
Terrestrial epiphytes
Terrestrial epiphytes are plentiful where there is frequent rain or fog such as rain forests (both tropical and temperate) and also areas like Florida, especially near wetlands, but some epiphytes are also found in drier areas. They could be vascular flowering plants such as orchids, cacti, or bromeliads including ball moss & Spanish moss. They include vascular spore-producing plants such as ferns. Almost 10% of vascular plants are epiphytic. Non-vascular, spore-producing plants such as mosses and club mosses are frequently epiphytes.
Since epiphytic life can be precarious, many of these plants have fine hairs or waxy surfaces to trap or keep water. Some collect water in-between their leaves, but others have adapted to water shortages by using the CAM or C4 method of photosynthesis that can take place even when all their stomata (leaf pores) are closed to conserve water.
Lichens, which are not plants, but 3-way symbiotic organisms (fungi, algae, & bacteria), are also epiphytes when attached to plants.
Strangler figs (Ficus spp.) are a special case: they are hemi-epiphytes when they begin life as a epiphyte high in the canopy, but when their aerial roots reach the ground, they are no longer epiphytes. It's a clever strategy, especially in rain forests where there is low light on the ground and the canopy is crowded. It's in the light when its young and it often takes over its host's spot in the canopy after strangling it by wrapping its roots around it.
(See below for more on terrestrial epiphytes.)
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| These barnacles, sessile animals (crustaceans), attached to a kelp stipe (stem above the holdfast), are marine epiphytes. |
Marine epiphytes
In the marine environment, plants, such as non-vascular seaweeds and vascular, flowering seagrasses, provide surfaces where sessile organisms can settle. Marine epiphytes include algae (micro & macro), bacteria, sponges, bryozoans, ascidians, protozoa, hydroids, crustaceans, & mollusks. They make their living from the nutrients and oxygen from the surrounding water, not from the plants. Sometimes, when there are too many epiphytes, the host plant may suffer from lack of light or lack of its own gas exchange.
