Temperature Requirements of Paphiopedilum Species

With a few other cultural hints

This writing came into existence after I had read (one more time) the old Rule:

Wrong!

Fortunately, there are many books written by many dedicated experts about the lady-slippers in general and the Paphiopedilums in particular. I am most grateful to all these authors and glad that I could read their instructions and arguments. I must point out that for the final decision, I am leaning on Catherine Cash’s writings and most heavily on Phillip Cribb’s second edition of “The Genus Paphiopedilum”; therefore you may not see all the earlier names listed.

As we know, the equator is an imaginary line around the widest part of the globe, right where the sun shines the strongest and temperatures are the hottest. The farther North and South we travel, the cooler our temperatures become. If we only had to consider the degrees of latitude, it would be very simple to deduce temperatures at any given point on earth. But we also have to remember that the higher an elevation rises above sea level, the cooler it becomes. We have seen pictures of high mountains in the tropics with eternal snow on their summits, like Mauna Kea in Hawaii and Mount Kilimanjaro in Africa. There are many other very high mountains in the tropics. And that is why it is not so simple to come up with a temperature for any given spot.

In addition, there is the weather to consider: the warm, wet monsoons, cool winters and dry seasons. There are also very shady river valleys and hot sunny rock faces. It makes a difference whether plants grow in full sun or on slopes or cliffs that are facing away from the sun. The biggest difference seems to be between continental climate and oceanic climate. You can see this clearly on distribution maps in several books that are so helpful to us – the amateurs.

Some of you may have seen the lovely chart: Supplementing Calcicolous Paphiopedilum Species, prepared by the Wellensteins, in http://www.ladyslippers.com/. The listing here is not as precise but it is an attempt to help a few growers who, like me, have trusted that old rule (above) and killed many precious plants. To make things easier, I am listing the plants in alphabetical order, for the sections and again for the species.

Please remember that new species of plants, including slipper orchids, are regularly discovered and described. Taxonomists are also constantly adjusting described species’ status from realizing that a new species may be closely related to an earlier described species and so they give the new arrival varietal status. Sometimes, species which grow over a large distribution area and have been found by several different plant hunters have been described under several different names and our taxonomists must decide which name has preference by being the first one published – and declaring the other names to be synonyms. I you own a plant, whose name does not appear on the following list, please try to look the name up in the pertinent literature, on the web and best of all: On the Kew List of Monocots.

As mentioned earlier, the most important factor affecting temperature tolerance is whether any species originate in continental areas with somewhat harsher climates which can present seasonally cooler temperatures or if they come from oceanic (coastal and island) areas with a gentler and generally warmer climate. Leaf colour is irrelevant. Most, if not all of the Paphiopedilum species grow intermediate, which means it is seldom below 15°C/55°F and no higher than 26°C/80°F. For short periods, plants may tolerate 36°C/100°F with good air circulation. A drop in night temperature is always advisable. During cooler temperatures, please ensure dry potting media. This also applies to hybrid Paphiopedilums.

Now to the species, grouped into sections, all in alphabetical order:

Section Barbata

This section is the largest; its vast area of distribution is mostly oceanic from SE China through all of Malaysia, Borneo, New Guinea and other South Pacific islands. The plants have mottled foliage and need intermediate to warm temperatures, even moisture and have no dormant period.

Section Brachypetalum

These are the warm-growing little “White” ones from coastal and oceanic areas spreading from SE China through Burma, Thailand and Malaysia. They all like extra lime in the potting mix and have patterned leaves.

Section Cochlopetalum

These have plain green, slightly tessellated leaves and come from Sumatra and Java – warm!

Section Coryopedilum

Plants come from the Philippines, Borneo, New Guinea – all areas of high temperatures and high rainfall; they all have plain green leaves.

Section Paphiopedilum

These plants come from a large area spreading out between S China through Vietnam, Thailand and India; they have plain green leaves and several have cool, dry winters

Section Pardalopetalum

This section has fewer plants but they are spread out over an area from SE China through Burma, Thailand and Malaysia to Borneo and the Philippines. They have plain green leaves, experience large temperature fluctuations; they often grow at high altitudes and are subject to the local monsoons.

Section Parvisepalum

This group comes from S China and N Vietnam and except for Paph. emersonii, they have strongly patterned leaves; all grow in a more continental climate.

Ingrid Schmidt-Ostrander - Canadian Orchid Congress