Also called air plants, Epiphyte plants are those that do not root in the soil but grow on other plants (mainly trees). Depending on their habitat, they may also grow on buildings and cables or wire. They depend on the things they grow on for support but epiphytes are not parasitic since they do not rely on them for nourishment. Since they do not grow in the soil they rely on the rain and air around them for nutrients, on some occasions they may even extract nutrients from debris that is accumulated around them.
Moisture is taken from the rain, air and sometimes the excess moisture (found mainly in pockets) on the plant they are growing on. However, epiphytes do make their own food in the normal way most plants do; using photosynthesis which is a process in which sunlight is used to make food and produce oxygen.
All major plant groups have epiphyte plants. The Temperate Zone houses many algae, lichens, liverworts and mosses while cacti, orchids, ferns and bromeliads like Spanish moss thrive in the Tropics. There is an estimated 30,000 species of epiphytic plants worldwide and more than half supposedly live in the rainforest. Most grow at very high altitudes however, epiphytic fungi, lichens, ferns, mosses and bacteria are exceptions to the rule. So too are aquatic algae like seaweed since they grow in the water and not in the air.
Epiphytes are highly adaptive, growing parts necessary and situating themselves in environments most susceptible to growth regardless of their habitat. Some will grow roots to help them attach to their hosts as well as structures that specialize in the collection and storage of moisture like scales and cups. And some, for example in Europe along the coastal fringes of the West may grow in the soil suspended in areas on trees. Epiphytic grass, small trees and small bushes are known to do this on rare occasions.
Epiphytes that grow in canopies (clusters of mature tree tops or crowns) benefit greatly from the excess sunlight and gain protection from many herbivores. Those in aquatic habitats form an important part of the ecosystem, serving as homes to anthropods, frogs and microorganisms that also serve as food for larger life forms.
The main problem with epiphytic plants is that they can be thick enough to overcrowd the plants they grow on hence causing damage. They have the ability to evade and take over the spaces of other trees. This is done mainly by large trees that start in canopies then gradually grow roots that travel down the trunks of the hosts until they overpower and replace the host. This process can take decades and once epiphytes become “free standing” trees they are classified as ‘hemiepiphytes’. New Zealand’s Northern rātā and the strangler fig are examples.
They also have the ability to remove the tree bark of the host (which is a protective structure) while growing roots. Since they grow in canopies, they can also lead to starvation of the host by blocking sunlight from its leaves prohibiting or hampering photosynthesis. Epiphytes due to their location can attract insects that can damage the host trees as well as increase the tree’s resistance to wind which can be detrimental in windy areas.
Despite these however, many species have adapted to their environment well enough to live symbiotically with their hosts causing no harm.