THE GENUS PAPHIOPEDILUM
Exactly how many species there are in the genus Paphiopedilum depends on to whom you speak. Excluding varieties and forms, it is commonly accepted that the number is between 65 and 70.
All Paphiopedilum, or Paphs. for short, are characterised by a cup-like lip reminiscent of a moccasin, or slipper, hence the familiar term “slipper orchid” or “lady’s slipper”.
Paphs. are mainly terrestrial (ground- or forest floor-growers) although a few, such as P. lowii, are usually found growing on the surface of rocks or perched in the cleft of tree branches. They are divided into two cultural groups; warm growing, mottled leaf types like P. Maudiae (ideal for beginners) and the cooler growing green leaf P. insigne types.
TEMPERATURE & HUMIDITYGreen leaved Paphs. ideally require a minimum night-time temperature of approximately 12ºC (55ºF) while the mottled leaved types prefer it a little warmer (16ºC, or 60-65ºF). Daytime temperatures should range between 22 ºC (70-80ºF) - however, short periods of higher temperatures will not harm the plants provided there is a good variation between night and day.
Humidity should always be around 60-65% during the day but at night such high levels should be avoided in case they lead to a possible onset of bacterial rot.
LIGHT & AIR MOVEMENTFor optimal growth throughout the year Paphs. enjoy a medium light intensity of about 1,000 - 1,500 foot candles. Direct sunshine should be avoided, except for early in the morning before it has any real strength. If the plants are being grown indoors do not place them on south- or west-facing window sills directly in front of the glass, as this acts as a magnifying glass and the plants will burn and dehydrate. Use a table or sideboard a few feet away, or cast some beneficial shade by the provision of blinds and/or net curtains.
Moist air and vigorous air movement at room temperature is highly recommended to keep plants healthy. It also helps to reduce the spread of disease by keeping the surface of the leaves dry. Be warned that hot and cold draughts can cause bud-blast (i.e., the buds turn brown, shrivel and die before they open).
WATERING & FERTILISINGPaphs. do not have pseudobulbs like Cymbidiums or Dendrobiums, and therefore must be watered regularly - no rest period required. Keep the compost moist (not wet!). Plants typically need to be watered every 5 - 7 days but growing conditions and temperatures affect drying out, therefore, you should modify this rule of thumb according to your own cultural setup.
It is recommended that fertiliser should be used at half the strength instructed on the pack. Paphs. are not greedy, like other orchids such as Cattleyas, Vandas, etc., and it is better to administer a weak feed regularly than to overdo the strength and only feed occasionally. “Weakly, weekly” is the thing to remember.
After 3 or 4 feeds, a flush with clear water should be introduced to leach out any possible buildup of salts in the compost.
POTTINGAs most Paphiopedilum are terrestrial they need a potting medium that will drain well but still retain some humidity around the roots. Too much water retention will suffocate and drown them. Large plants will take a coarser grade than seedlings but the ratio of the mix is the same for all - i.e., 4 parts bark to 1 part perlite. Some growers also add charcoal to the mix to keep it sweet, but this is not strictly necessary.
Repot your Paphs. before the mix has broken down completely, and before the plant grows too large for its current pot. Very large plants would also need repotting when they are divided. An annual repot is advised, orcertainly every eighteen months. This procedure entails first removing any dead roots, then positioning the plant in a new container with its crown level with the rim of the pot, and finally filling in around the roots with compost until the level reaches a little above the base of the plant. Do not bury the new season’s growth as this will cause it to rot. The base of each growth, or “fan”, should be in contact with the growing medium to encourage new shoots to form.
Recently repotted plants should afterwards be placed in a shady area and eventually moved back to normal conditions once they have settled. Restrict watering to a minimum until new roots are apparent, but be sure to maintain good levels of humidity and air movement to assist the plant through what is virtually a stressful period, until it has become established.
And above all, enjoy your Paphs.!
By courtesy of Paul Philips from Ratcliffe Orchids Ltd www.ratcliffeorchids.co.uk.