Paphiopedilum Pfitz.
(Lady Slipper Orchids from Asia and the Pacific Islands)
There are several kinds of lady slipper orchids:
There are two groups of lady slippers in Central and South America. The ‘Selenipediums’ which usually are not found in amateur collections; they need very hot and humid conditions, their flowers last only a short while and the plants can reach a height of over 15 feet (3 meters). The other group is called ‘Phragmipediums’ and while they are quite popular, they are not the subject of this lecture.
And there are the ‘Paphiopedilums’.
The slipper orchids commonly found in the collections of hobby growers are the ‘Paphiopedilums’. They grow over a vast area: from India in the West through most of China, down through Malaysia, to New Guinea and all the way to the Salomon Islands. If you can picture a map of this area, you will realize that all of it lies in proximity to the equator. There is a theory that the primal centre of distribution of Paphiopedilum is in New Guinea.
 Paphiopedilum display |
This means that Paphiopedilums grow in very warm places. It used to be said that they all need to grow intermediate, the plain green-leaved Paphs even cold. Not true! Of course, some of the older hybrids – the Paph. Winston Churchills etc. were bred with P. villosum, P. spicerianum and others that grow in cooler areas of Northern India. These plants would tolerate cooler temperatures, especially during winter. In general, I find that all my Paphiopedilums like to be warm, some more so than others. At night the temperatures should always be several degrees cooler than in the day – except baby plants – they need to be kept warm.
It also used to be said that these plants don’t need much light. Wrong again! Without sufficient light, you will not get flowers on your orchids – in fact on any plant and yes, even Paphiopedilums need good light. Remember they live in the tropics. You may want to keep very strong, direct sun off the leaves, just like you protect your Cattleyas from too strong summer sun. I have noticed that even the mottled-leaved paphs can take a lot of light without fading of their attractive patterns – just don’t burn them, please! and keep in mind that good ventilation will go a long way towards keeping the leaf temperatures safe.
For all vegetation, in our Northern latitudes, the main growing season goes from March to September; this also applies to the Paphiopedilums. At this time, the plants need sufficient water to stay evenly damp in the root zone. During the short dark days of winter, they need much less water. If you fertilize your paphs at all, give them a very weak solution and none in the winter. In Victoria, we have very nice water that is (like rainwater), somewhat acidic. Once in a while, I apply weak doses of Calcium Nitrate to change the pH of the mix so that the roots can better absorb some fertilizer. Please do not give any lime feeding to the Paph. delenatii – they do much better with rainwater. Farther East (Okanagan and beyond the Rockies) the water contains enough lime and you won’t have to supplement with Calcium. Then Paph. delenatii might become stressed. There is a wonderful listing from Antec Laboratories (Bob & Lynn Wellenstein) about Calcium for Paphiopedilums. In this list, each species has its requirements spelled out. Of course, the need for water depends on the potting mix and its age. A fresh, loose mix of coarse particles will dry out faster than a fine mix, especially when it is old and has started to break down. In this case, you really should re-pot, at any time of the year. I prefer to pot my plants early in the spring, before the new roots have grown too long; then the plants will have all summer to grow in the fresh mix and should be alright for at least a year or two. Very small plants in small pots need to be moved more frequently and very large plants may keep inside their big pots for several years. But eventually, some of the old roots will die off and they will exude harmful substances into the mix. In these ‘captive’ conditions, we have to uproot the plants to keep them healthy.
If during handling, a piece of the plant breaks off, with some roots attached to it, you can pot it up separately. However, I strongly recommend that you keep your orchids in as large a clump as possible. You will get better flowers and more of them – after all, that is why we grow these things – right? When you look at a large plant of Paphiopedilum (and Phragmipedium), you will notice around the outer base several young plants. Look closely: they are attached to the mother plant with a rhizome and they do not have any roots! In fact, they may not have good roots for several years – taking all their food through the mother plant. It was a particularly sad experience for me to first pot up all those little runner plants of a good-sized P. armeniacum, only to have them all die; their little stubby root tips were not long enough to support the young plants.
When a flower stem begins to grow up, start staking it carefully and be sure that the light source(s) will always come from the same direction to avoid growing a zig-zag stem. For showing, tie the mature flower neatly with the staminode securely against the support so that it looks straight at you – the stake must not show above the flower. On a young plant that is flowering for the first time, I just let the flower open to see what it looks like and then cut it off. It will keep in a vase for a while and the young plant will grow much better without having to support a bloom. If ever you want to put a seed-pod on your Paphiopedilum, be certain that the plant is strong enough to hold the pod for the required ten months (this time period applies to Paphiopedilum seed pods). It is an enormous strain on any orchid to grow seeds and only a strong plant will survive.
I have found that the slipper orchids do not get many bugs. Sometimes, there may be aphids but as long as you are observant, you can take care of these little worries before they become big problems.
Ingrid Schmidt-Ostrander - Canadian Orchid Congress