The following focuses on plant habitats, and in particular how they affect orchid culture in this country. One facet of natural habitats for most of the orchids grown in this country is significantly different from the conditions naturally experienced here, and this will be highlighted, together with other significant aspects.

INTRODUCTION

IF ONE LOOKS AT ORCHIDS GROWING NATURALLY AROUND THE WORLD, one can see that there are several types of habitat where they make their homes. It is interesting to look at these, as we can gain from this an increased understanding of the plants, which in turn can facilitate our successful growing and flowering of those orchids. The discussion is in a wider ‘macro’ sense, but will, I hope, highlight the features of the main zones, and emphasise in one particular facet that our climate significantly differs from the natural conditions experienced by most of the orchids we grow. Most of the cultural ‘rules’ we have originate from differences in the natural plant habitat, and groupings such as ‘warm’, ‘intermediate’ and ‘cool’ are based on natural habitat information. If you understand habitats better, you will better understand the requirements of your plants to grow them to their full potential, and perhaps even be able to more easily solve cultural difficulties whenever these are experienced.

A number of people have discussed habitats on a generalised basis, and the distinctive features of each one are significantly related to geographical form and altitude and climate. Before looking at the habitats it is, however, worth noting that orchids can be found in virtually all areas of the world in varying concentrations, with epiphytic orchids mostly concentrated in the warmer tropical areas, and terrestrials predominating in high latitude and higher altitude tropical habitats, although are not confined exclusively to these zones.

Orchids are not found in the polar regions, mountainous habitats above the permanent snow line (approximately 3,500 meters above sea level at the equator) or the most severe of deserts. The word ‘severe’ should be noted as even in what is otherwise considered a harsh dry arid environment, orchids will often be found around water seepages, and in gullies and other locally protected environments. Orchids have in some cases developed remarkable adaptations to survive very difficult habitats.

The habitats that can be readily identified are:-

  • In tropical areas
    • tropical lowland rainforest having a hot humid climate
    • foothill ranges subjected to the seasonal monsoonal climate, and
    • savanna and prairies, arid deserts, usually in ‘rain shadow’ localities experiencing a hot dry climate, and
  • in tropical and temperate areas
    • tropical high altitude areas and
    • high latitude localities          both of which experience cooler and harsher climatic conditions

The diagram which follows may assist in understanding certain characteristics of these regions. This geographic profile can be seen in New Zealand if one takes a cross section of the South Island from the West Coast to Canterbury, although obviously the tropical monsoonal conditions are not experienced there.

The predominant wind comes from the oceans, carrying much moisture. There are vast areas of forests and open water areas on land which all transfer huge amounts of additional amounts of water vapour to the already heavily saturated atmosphere. In lowland areas and basins, temperatures are high, with humidity always near saturation level. In areas where there is some air movement, for example along rivers and clearings, orchids are found, although where there is stagnant air, orchids are generally absent. This comprises is the lowland rainforest habitat

The major orchid habitats are subject to the summer monsoons, which affect particular countries from early summer to early autumn. The hot humid air is blown inland, striking mountain ranges lying across the direction of the prevailing winds, which forces the warm most air upwards. As the air rises, it cools and the water vapour it contains starts to condense, and a vast quantity of rain falls on the mountain slopes, especially with increasing altitude. The foothill mountain forest habitat is generally considered to extend from 850 to 1850 metres above sea level. It is the most significant of all habitats, as most of the popular orchids are natives of this zone, some 60% of all orchid species living within this habitat.

At the higher levels above some 1850 metres altitude mists and fogs are persistent, and this is the high altitude tropical habitat. The permanent snow line in the tropics is over some 3,500 metres above sea level sets the upper level where orchids will be found. The conditions here are also typical of the high latitude countries such as New Zealand.

As the air passes over the mountains, and falls to lower altitudes, it warms again and att he same time dries. It has, however, lost most of its moisture on the mountains, and the typically inland arid prairies and savannas will be drier and hotter, providing an increasingly arid environment, the fourth of the main habitats we will discuss.

The specific habitats will now be discussed in detail.

SUBJECTS ARE LISTED IN THE LEFT INDEX WINDOW.

CLICK OF RELEVANT ITEM WHICH WILL BE SHOWN IN THIS MAIN WINDOW.

Site establi

If you wish
you may

E-mail
me at -

powwebmaster
@ihug.co.nz
 

shed 9th May 1998