Introduction
New Guinea orchids are on average neither more difficult nor easier to please in cultivation than those from other regions. Their requirements are however far from uniform so it is difficult to give general guidelines. Some parts of New Guinea experience a true dry season, and this should be reflected in the cultivation of species originating from such areas. However, for most of New Guinea it can be stated that there just is a wet season and a wetter season. Long droughts are exceptional and when they occur many orchids are killed. In most areas the yearly rainfall is about 4000 mm and may exceed 8000 mm locally. The first figure corresponds to about 11 litres of water per square meter per day. That is a lot of water. This does not imply that the average New Guinea orchid should be imagined as growing in a swamp. Even in the wettest areas, such as the upper montane cloud forests, it will not usually rain twenty-four hours a day, and few days will pass without any sunshine at all. Epiphytic orchids in the lowlands and those growing high up in the trees in the mountains frequently have to cope with several hours and on occasion several days of desiccation. Yet others grow in the protective fur of living mosses that envelopes the trees especially at high altitudes, and these orchids can be very intolerant of drought. For terrestrial orchids it is even more difficult to state general rules, as here not only altitude and exposure, but also soil type and drainage are factors to be taken into account. A gross simplification is to divide the terrestrials into forest plants, requiring shade and a humus-rich soil, and grassland plants, requiring sunshine and often a more mineral soil.
Even closely related species can vary greatly in their response to the conditions in cultivation. Mediocalcar decoratum ( 0436-21A.JPG) grows like a weed in any cool humid greenhouse, but M. geniculatum ( OR18-036.JPG) increases very slowly and rarely thrives away from its native mossy forest. Dendrobium forbesii ( OR14-063.JPG) is easy to grow, the fairly similar looking D. engae ( OR14-058.JPG) is quite a tricky plant. Most species of Pedilochilus ( OR10-071.JPG) are difficult to grow for no apparent reason.
Sometimes it is fairly obvious why certain species fail to survive in cultivation. This is true for the leafless terrestrials that are often called 'saprophytes'. If they really were saprophytes, that is, organisms capable of decomposing organic matter,
then they would perhaps be easy to cultivate in a big pile of leaf litter. In fact such orchids are parasites on fungi, which is quite a different situation. Difficult to grow, even to keep alive, are also the subalpine orchids, comprising roughly those species occurring above 3000 m altitude. They require a combination of low temperatures, high light intensity, lots of moisture, and plenty of fresh air, which is very hard to realise in a normal greenhouse. It is a great pity that some of the most attractive New Guinea orchids belong to this category, such as Dendrobium brevicaule, Dendrobium dekockii.
To leave potential cultivators not entirely in the dark we have attempted to assign each species in the checklist to a category which gives at least a clue to its cultivation. Some species could well have been admitted into more than one category, but in such cases only one has been chosen. To give just a single example, the lovely Dendrobium cuthbertsonii; for many growers their favourite New Guinea orchid is usually found as an epiphyte in montane forest but may also occur in open turf and on steep road banks. In the checklist it is only listed as a cool growing epiphyte.
Warm growing means: day temperatures between 25 and 30 °C and night temperatures between 18 and 20 °C; intermediate growing means: day temperatures between 22 and 27 °C and night temperatures between 15 and 18 °C; cool growing means: day temperatures between 16 and 21 °C and night temperatures between 7 and 13 °C.
Alternatively, these indications can roughly be translated into altitudinal ranges:
- warm - below 500 m above sea level (asl)
- intermediate - 500 to 1800 m asl
- cool - above 1800 m asl
A final note of warning: when a species is said to require cool conditions and high light intensities it will definitely need some shading in cultivation when the temperatures cannot be prevented from reaching 23 °C or more!
Relax - You can do it!
There are no 'cast-in-concrete' rules for orchid care. Correct culture for each and every climatic zone is different but some basic guidelines are applicable to all of them. The first order of the day is : Do not panic! Looking after orchids is supposed to be (and is) a relaxing activity. Orchids are slow growing plants at the best of times and changes in culture, fertilization, watering habits, temperature and potting mix will only show up much later. So do not expect overnight changes in your plants.
Orchids, generally, like the same environment regarding temperature, light and humidity, as humans do. We do not like to be hot (bright sun), wet (rain) and we like a temperature in the mid-twenties to be comfortable. Some orchids can stand full sun and others need some shade in order to do well. Most orchids however, do best in broken shade during the heat of the day, full morning and afternoon sun will do most of them no harm.
Find a place in your garden, balcony or terrace where you would like to spend some time, and your orchid will be comfortable there. If your orchid came in a pot find a secure and appropriate place, such as a bench or a tree, or make up a wire hanger and hang it on a trellis or one of the lower tree branches.
Orchids that have recently been acquired, with bare roots, broken pseudobulbs (stems, canes) and generally do not look too promising of things to come, you should do a bit of cleaning up. With a sharp knife or a pair of secateurs, cut away the broken pseudobulbs, trim off roots and old flower spikes. Now that the plant looks a bit more tidy, you can either pot (never use a pot without holes) it or tie epiphytic orchids to a tree, a piece of wood or tree fern. Once you have established your orchids in an environment that suits them they should best be left undisturbed and stop fussing. Do not worry unduly as orchids are among the hardiest plants known. They are actually quite difficult to kill. Concentrate instead on watering and feeding them correctly.
Orchids like to be 'wet and dry' meaning that you should water the orchids that you grow in full sun, every morning before the sun gets too hot, so that they can dry off within a couple of hours after watering. Give them a lot of water, not just a sprinkle. Orchids love high levels of humidity and we are fortunate that this part of orchid care is being looked after by our climate.
Healthy roots = healthy orchids
Take good care of the orchid roots! 
Healthy roots for epiphytic orchids look silvery with a light green growing tip when dry and dark green when wet. Unhealthy roots from overwatering look brown and shrivelled and will NEVER recover.
Orchids are very slow growing and therefore you cannot expect things to happen quickly. Within a few weeks however, you should see healthy new roots, silvery white with green tips appearing, clinging to your artificial tree, the piece of wood or tree fern or spreading in the pot. The leaves should be of a healthy green colour, not yellow or brown and should be tough and leathery.
Normally, all you have to do apart from watering, is to feed them a little fertilizer and check for those little nasties, like snails and cockroaches and other insects, particularly for those that like to bite and disfigure them like grasshoppers and beetles. We do not want any of those and will need to spray them weekly with an insecticide if insects are a problem.
Enjoy your orchids, watch them and get to know them. You will find that orchid growing is a most rewarding and relaxing hobby. There is no need to worry, just be happy!
The Right "Pot" and Potting Medium
All pots in which we grow orchids must have extra drainage holes, as we will want the water to run through the medium rather than stay in the pot. Any type of plastic pot will have to do. Given a choice, you select a 'squat' pot that is only as high as its diameter at the top, has many holes at the bottom and a raised center, known as 'azalea' pot. The pots we buy should be of uniform size and we make some extra holes with a soldering iron, if necessary. Never ever place an orchid in a pot without holes!!
That is a sure way to kill your plants!
Orchids never grow in soil, even terrestrial orchids have their roots only buried in the leaf litter. Therefore the right potting mix is a medium which lets water run through freely allowing the orchid roots to dry off and breath. Charcoal from hardwood, orchid bark or coconut chips are most suitable. Broken clay pipe is most UNSUITABLE. The potting mix is only required to give the roots anchorage. Growing good roots is the most important aspect of orchid growing!!
Light and Air
Place your orchids in the garden or greenhouse according to their light requirements. If you are unsure about the light requirements of a plant, it is safe to keep it in a shaded area at first. Once properly established, you can gradually move it later to a brighter spot in the garden or greenhouse. Good air movement is essential for the well being of your orchids. A gentle breeze is all they need. Air must get into the potting mix to keep the roots healthy.
Watering
Water thoroughly every morning or evening during the dry season. Orchids grown in the garden will not require extra watering during the wet season. Orchids grown under cover should be watered 2 - 3 times a week during the wet season. On very hot days we might have to water in the afternoon as well. This is best done during mid-afternoon as we want the plants to have dried off by nightfall. Anyway plants should be dry within about two hours after watering. Never water during the heat of the day, from 10.00 am in the morning to 3.00 PM in the afternoon.
IF IN DOUBT, DO NOT WATER!!!
Feeding
Use a 'balanced' fertilizer (with equal parts of NPK (nitrogen, phosphorus and potassium, the label should read 20:20:20 or nearest combination) at recommended strength once or twice a week. Two level dessert spoons (30 grams) diluted in 8 liters of water is about right. You can mix most insecticides or fungicides with fertilizer. You are not helping the plant in any way by fertilizing heavily as orchids cannot absorb nutrients quickly. Spray the fertilizer mix also under the leaves as that is where the orchid feeds.
Pests
Provided insect pests are a problem, spraying is recommended weekly. Alternate between a systemic and an organic insecticide. Ensure that you spray under the leaves and the top of the potting medium. The more common brands available are suitable for a variety of insect pests. Read the label. Snails, which can chew off tender new shoots in one night, are treated with snail bait spread on the ground or bench tops. Clean up all debris around your orchids.