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Epiphytes – Wonderful Garden Plants

Backlit Stag Horn Fern

Backlit Stag Horn Fern

Epiphytes are remarkable plants that have evolved to grow on the branches, trunks and leaves of other plants without deriving nourishment from their host plant. They make no contact with the soil. Moisture and nutrients are absorbed from the air and from the decay of accumulated humus, which includes animal droppings. The basket-like growth form of many species serves to capture and hold leaf litter, e.g. Birds Nest Ferns, Basket Ferns.

Some epiphytes may also be found growing on rocks and are called lithophytes. In this situation they are an agent in the weathering of rocks. Minerals released during this process contribute to the lithophyte’s nutrient supply.

Plant and plant-like groups that exhibit the epiphytic habit include cacti, bromeliads, orchids, ferns, mosses, lichens and liverworts. Of these cacti and bromeliads are not natives of Australia.

All epihyhytes are regarded as special life forms for the purposes of plant community classification. A broad division of epiphytes into vascular and non-vascular is helpful in separating various types of rainforest. They are distinguished as follows –

  • Vascular epiphytes have a well-developed system for transporting water and sap (cacti, bromeliads, orchids, ferns).
  • Non-vascular epiphytes are without such a specialized system (mosses, lichens and liverworts).

The presence of large vascular epiphytes is a characteristic of tropical and sub-tropical rainforests. Non-vascular epiphytes predominate in warm and cool temperate rainforests with vascular epiphytes being rare or absent.

Many of the vascular epiphytes make attractive garden specimens and are widely used in cultivation.

Hemi-epiphytes

In some cases a vascular plant may begin life as an epiphyte, but eventually make contact with the soil and the plant becomes self-sufficient, e.g. strangler figs. These are primary hemi-epiphytes.

Strangler Figs have a remarkable growth form and reproductive process involving fig wasps.

Some hemi-epiphytes begin life in the soil but later, after growing up tree trunks, lose contact with the soil and become epiphytes. These are secondary hemi-epiphytes.

In Australia, Pothos longipes of the Arum Lilly family, is classed as a secondary hemi-epiphyte. It can be seen coating the lower trunks of trees in moist mountain forests where it may cover most of the tree trunks. It occurs in subtropical and tropical rainforests.

Vascular Epiphytes

Vascular epiphytes are of two groups. One reproduces by spores (Ferns) and the other by flowers and seeds (Orchids, Bromeliads and Cacti).

Ferns belong to a special group of plants that reproduce by spores rather than seeds and exhibit the epiphytic and lithophytic habit. The spores are produced in spots or lines (sporangia) on the underside of leaves. They vary in size and formation from tree ferns with large woody trunks to delicate, filmy specimens. Whilst they are generally thought of as moist habitat species there are many that exist in dryer habitats. Ferns with an epiphytic life habit include Stag and Elk Horns, Hares Foot Ferns, Basket Ferns, Birds Nest Ferns, Basket Ferns, Pyrrosia and Finger Ferns. Most are also lithophytic and some such as Basket Ferns can be found in drier open forest habitats.

Smaller species of Finger Ferns and Pyrrosia have single leaf blades arising from creeping stems (rhyzomes). Pyrrosia occur as epiphytes and lithophytes and can be found in drier habitats.

Orchids are attractive flowering plants, which have a varied growth form. They range in habitats from ground dwellers to those with an epiphytic/lithophytic life-style. The epiphytic/lithophytic forms have adaptations for such exposed habitats e.g. fleshy, swollen stems, often bulbous at the base that can store water and nutrients, and roots that can absorb moisture from the air.

Non-Vascular Epiphytes

Mosses and liverworts are lower life forms superficially resembling plants. They also reproduce by spores, but differ from ferns in lacking a vascular system for fluid transportation.

Lichens are a compound life form made up of a fungus and an alga. They can be seen on the leaves, branches and trunks of trees, and on rocks. They tend to predominate on the southern side of trees in the Southern Hemisphere (northern side in the Northern Hemisphere). In the absence of a compass, this growth habit can be used in navigation to provide a rough indication of North/South.

Out and About

There is much to see either side and above the walking track to make your walk more enjoyable. Keep an eye out for epiphytes and hemi-epiphytes – see how many growth forms you can identify (binoculars are handy). If walking in rainforests pause occasionally and look up in the forest canopy for epiphytes especially if there are fig trees present. Examine rocks and the southern side of tree trunks for non vascular epiphytes, look into the forest for hemi-epiphytes (Strangler Figs and Pothos longipes).

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