Tuesday, December 27, 2005

ORCHID GROWTH TYPES


Orchid Growth Types—Epiphytes, Lithophytes, Terrestrials

People who are new to orchids sometimes think that orchids are parasitic plants because the pictures of them growing in the wild often show the plants growing in trees

Epiphytes


Epiphytic orchids live on trunks and branches of shrubs and trees. It is a widespread misconception that orchids are parasites: orchids cause no harm to their host and use them for support only. Epiphytes receive nutrients from the air and from small bits of detritus left by birds and dead plant material. They depend on rain and mist for their water supply. The main advantages for epiphytes are less competition with other organisms, a better light supply and better protection from parasites, diseases and fire. To overcome water-stress most epiphytes have developed adjustments, enabling them to store water, such as succulent pseudo bulbs or fleshy leaves. There are many different host plants, they are mainly chosen because of their structural and chemical bark features. Many species show particular preferences as to the type of host and often are localized in their occurrence.

The majority of orchids grown by man around the world are Epiphytes. Many are grown mounted on wooden rafts such as cork; some are grown in baskets; and some can be grown in pots in an extremely porous mixture of bark, perlite and charcoal. Dendrobium (M’sia largest export of cut flower), Tiger Orchid (world’s largest) and Taeniophyllum (world’s smallest) are common examples of epiphytes.

Lithophytes

It is relatively common for epiphytes to also grow on rocks which provide no nutrients to the plant. There are also many orchids which do not grow on trees at all, but only on specific kinds of rocks. These plants are called Lithophytes. The term comes from the Greek words, litho-, meaning stone and phyte, a plant--thus a plant that lives on stones. Often they are found around the bases of trees or in crevices on rocky hillsides where pieces of debris collect. An example of lithophytes is Sophronitis.

Lithophytes orchids grow on rocks. The surface of rocks seems to provide a good place for germination and attachment of seedlings. Only a few orchids are exclusively lithophytic, most will also be able to develop as epiphytes or terrestrials.

Terrestrial

Terrestrial or ground orchids are rooted in soil; they occur in different types of habitat (forest floor, grassland, woodland) and at altitudes from sea-level up to 3000m. Many of them are deciduous which means that the plants loose their leaves and have a dormant period in which no growth occurs. The underground parts (tuberoids) store food reserves to ensure the development of new shoots at the beginning of the next growing season. Other species are evergreen. Examples of terrestrial orchids are cymbidiums and most of the slipper orchids.

Some terrestrial orchids do not have any chlorophyll, they get their nutrients from dead and rotting material, these are called saprophytes.

Due to their specific requirements orchids are good indicators of the ecological state of an environment. They can only grow well in unspoiled places and die quickly if their environmental conditions change. Epiphytic species are mostly confined to tropical regions while terrestrials are more widespread in cooler areas.

*WENDY*