What are epiphytes?
Picture the thick, lush rainforests of the Amazon with it’s towering trees and large green foliage. The wet, humid conditions; with water running off the palm leaves, and colourful frogs perched on the slippery branches. It’s a dense, moist and tropical jungle. Everywhere you look there is greenery, from the bright neon greens of the ferns to the dark, yellow-tinged greens of the moss growing on the trunks. The forest floor is a combination of soggy leaves and debris. It is dark, damp and swampy on the ground.
But looking closely up at the rainforest, especially at the branches, you’ll notice that there is more to them than just the canopies and leaves. The trees are forests themselves, covered in a dense tangle of living organisms and plants.
On these large branches, there’s a collection of soil and decaying matter. Fallen leaves, organic decay, dust and bark collect in the forks and crevices of the mighty trees, creating pockets of habitable areas. Seeds, blown into this organic soil mix, from the wind, or deposited by birds and other animals, germinate and grow. These plants are called epiphytes.
Epiphytes are plants that grow on another plant (a host) and take in their nutrients and water from the moisture in the air, rain or decaying matter accumulating around it. They use the host plant as a foundation or base, either for protection against the dangers on the ground floor or for better positioning in order to get more sunlight. Epiphytes are not typically parasitic, and do not aim to harm the host plant. Unlike a parasite which takes its nutrients from the host plant.
This incredible array of plants dangling out from the trees, rock crevices and vertical supports are epiphytes and they number around 30000 species worldwide. Some of the most popular epiphytes are bromeliads, ferns and mosses. The adaptation of these species of plants to become epiphytic allow them to flourish in areas where the ground is difficult to reach or already populated by other plants. Not all epiphytes grow on trees; species like moss and lichen can grow on rocks, walls and other inorganic surfaces.
The Bromeliads ( Bromeliaceae)
This is a family of plants consisting of around 3475 known species. They are mostly native to the tropical Americas, however, a few outliers can be found in the subtropics and one in Africa.
The foliage of the Bromeliaceae grows in a rosette (a circular arrangement of leaves ) and is widely coloured and patterned. The inflorescences ( stem and flowers ) of this family are often more diverse than any other plant family. Some flower spikes can be as tall as 10m and retain their colour for up to 12 months. Epiphytic Bromeliads only grow roots for support, whilst terrestrial plants use the root systems to obtain water and nutrients from the soil. A good example of an epiphytic Bromeliad is the Tillandsias. They are commonly referred to as air plants. There are 1814 species in the Bromeliad family that are epiphytes ( these include the 650 species from the Tillandsias). Air plants have a further adaptation in their epiphytic nature by developing trichomes on their leaves. A trichome is a fine hair-like outgrowth that absorbs moisture and reflects the harsh light.
Other Bromeliads collect water in their centres. These are referred to as phytotelmata. This pool of water attracts organisms and allows for micro-habitats to exist. The water provides hydration, safety, breeding for organisms and even homes for other Bromeliads. The diverse range of invertebrates using the water also release nitrogen into the pool, of which the plant benefits from.
This pool of water is an adaptation by the plant through which it’s leaves are tightly bound to capture any rainwater or condensation forming this tank.
Some of the common organisms that use the water tank of the plants are salamanders, tree frogs and even crabs.
Orchids ( Orchidaceae )
There are around 22 000 species of orchids around the world. Many of which are epiphytic in nature (70%). The plant can be recognized by its symmetrical flowers with male and female organs fused ( stamens and carpel ), and a modified petal. The leaves usually have parallel veins. Many orchids are endemic to micro-regions, such as an Andean valley or a single canyon of trees. They are adapted for epiphytic life because of their large surface area of roots, which can rapidly absorb water and nutrients. Their secondary stems can store water for prolonged periods of drought. Another reason for their success is that they produce tiny seeds ( in the hundreds of thousands) which are balloon-shaped and blow easily for dispersion.
Epiphytes produce more seeds than terrestrial species because so many seeds fail to reach suitable growing places. The seeds are often adapted for wind dispersion by having wings or gliding attributes. Birds eating the seeds are likely to deposit them as faeces on tree branches.
The cacti found in the rainforests are rather different from the typical, succulent, spiky ones found in the desert. The cacti in the desert regions are outfitted with waxy leaves to reduce water loss. They are protected by sharp spines. Epiphytic cacti, however, often lack these traits and are adapted to live in the trees by having elongated leaves for light absorption, not water retention.
There are 19 species of epiphytic plants in the cactus family and they are referred to as epiphyllum.
This group of plants is most commonly known for their large green leaves and habit of growing in moist areas under forest canopies. Ferns reproduce via spores instead of seeds and do not flower. Epiphytic ferns collect masses of hummus, which provide nesting sites for many species of arboreal ants and other invertebrates. The epiphyte’s roots grow around the host plant, giving anchorage and contact with the stem and branch. Dissolved chemicals in the rainfall water are trapped by the roots as water runs down the bark of the host. The epiphyte’s roots obstruct the flow thus reducing the rate of erosion caused by the waters and thereby allowing accumulation of considerable quantities of debris.
Epiphytes in South Africa
There are several species of epiphytes that can be found in South Africa. These plants are found in the wetter, more humid areas of the country. Many of the large tree branches are covered with epiphytes such as Peperomia, ferns, mosses and lichens (that after rain or fog are bright green, but in dry times all but the Peperomia are shrivelled and brown waiting for moisture). Also, many of the exposed branches are festoon with the Old Man’s Beard lichen (Usnea cf barbata). Woody climbers of lianas are locally common, and where they occur in dense concentrations the local birds seek refuge in the dense cover. A very common host plant in South Africa is the Raphia australis ( Palm tree).
Epiphytic orchids can be found growing on trunk branches along the southern coastal region of the Western Cape, Eastern Cape and KwaZulu-Natal. There are also several orchids in Mpumalanga and Limpopo. There are no epiphytic orchids in Cape Town or the Karoo.
The epiphytic orchids of South Africa are predominantly located in dense forest regions near streams of water. In total there are 56 epiphytic orchid species in 20 genera in South Africa. Representing only 12% of the total orchid population of the country. Popular orchids that require no soil but can be mounted readily are Ansellia africana and Mystacidium capense.
Unlike most orchids, the epiphytic plants of South Africa have small, less noticeable flowers. The best way to identify the plant in a tree or cliff would be from looking out for their whitish roots.
Epiphytes as House Plants
When growing an epiphyte it is important to research how big the plant is going to grow.
When growing a large specimen you want to ensure that you place it in an area ( a fork of a tree or large branch) that can support its growth. It is important that the plant does not move about until new roots have developed and secured it to the host or mount. One can use an old cloth to strap the plant onto the mount or branch.
Plants can be grown on anything from cork, bark, a rock crevice, a living tree or a wiring board.
The plants should be watered sparingly until new roots appear, after which an occasional spraying with a liquid fertilizer will benefit the growth of the plant. For specific instructions on air plant care see this article.
Remember that each epiphyte has it’s own unique growing conditions and it is best to understand those before making a purchase. Some plants require frequent waterings and humid conditions.
These would be specialist plants. A good way to understand the plant and to see if it would be a good fit within your home or garden is to look at its natural growing conditions.
In general, plants should be watered frequently in the hotter seasons, whilst in winter the plants go dormant and require much less attention. Plants mounted on wood or cork do well because they are not allowed to sit in water. Plants, especially Tillandsias, may begin to rot if water is allowed to sit in the leaves or base. Adequate air flow helps to dry the plant out. Humid conditions often supply the plant with sufficient moisture from the air.
Epiphytes are an amazing group of plants and show their resilience and adaptability to the elements. They break away from the traditional idea of plants needing soil and ground and show that these species can literally grow wherever. Next time you are out driving or in the park take a look around. You will be surprised to see how many little plants are growing on a rooftop, a tree branch or along a wall.