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This article was originally printed in 1995 in the American Orchid Society Bulletin, 64(7): 738-741.
Its habitat and culture.
Charles and Margaret Baker
Paphiopedilum armeniacum was introduced to western cultivation in 1979. Its' introduction created amost instantaneous interest and excitement which has continued throughout the intervening years. The large, round, clear yellow flowers are beautiful and unique to the genus. The plants' beauty is enhanced by the strongly marbled leaves with the dark and light bluish green tesselations on the top surface and dense purple spotting on the underside. Unlike many orchids, it is an attractive plant even when out of bloom.
Although it has been given broad and frequent coverage in many publications, very little factual information has been available about its habitat. Cultural instructions have ranged from warm to cool growing with nearly every possible combination in-between. By the mid to late 1980s, the late Dr. Jack Fowlie reported the habitat location in The Orchid Digest, but he was unable to the provide the elevation. Armed with Dr. Fowlie's verbal description of the region in which the plants were found and topographical maps of the area, we estimated the habitat elevation at about 3000 ft. (910 m). Calculating temperatures for this elevation resulted in temperatures consistent with those recommended by Lance Birk in his excellent work, The Paphiopedilum Grower's Manual. So we cautiously recommended winter lows of 40-43°F (4-6°C), even though others were recommending much warmer winter conditions. We felt that our recommended temperatures were reasonably close to habitat conditions. Because we are always uneasy about recommendations based on estimations and assumptions however, we continued our search for the elusive habitat elevation.
Then suddenly and unexpectedly, through no effort on our part, the search was over. On a trip to China, a friend found a recently published book titled Orchids, which she loaned us. The book includes a color photograph taken in the habitat and brief discussion of 180 orchid species found in China. Since it has no index, we leisurely leafed our way through it, and suddenly there was the answer! P. armeniacum was pictured and listed as growing at 6550 ft. (2000 m) in the exact region Dr. Fowlie had reported.
With this information, we are finally able to offer, with a high degree of confidence, the climatological conditions under which this species grows in nature. We do not suggest that these are the only conditions under which the plant can be cultivated. If it is already growing and blooming, then don't mess with it, regardless of what any "expert" suggests. However, if a plants' requirements are unknown when adding it to a collection, or if it is not growing as well as it should, then the climate data from the habitat offers a basis for providing the approximate conditions that will ensure success. Growers are reminded that changes should always be made slowly.
Paphiopedilum armeniacum grows in a remote area of southwest China near Bijiang in western Yunnan Province. Plants are found on limestone hills and cliffs in forests above the Salween (Nujiang) River near the border with northeastern Burma at about 26.5°N Latitude. They grow at about 6550 ft. (2000 m) among rocks in semishady mountain forests. The nearest weather station is about 95 miles. (150 km) away. It is located above the same river valley at about the same elevation, so conditions should be essentially the same at the two locations.
CLIMATE: Station #56748, Pao-Shan, China, Lat. 25.1°N, Long. 99.2°E, at 5554 ft. (1693 m). Temperatures are calculated for an elevation of 6550 ft. (2000 m), resulting in probable extremes of 87°F (30°C) and 25°F (-4°C).
N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 59 60 67 73 74 75 74 74 73 70 64 60 F AVG MIN 32 36 40 46 55 61 62 61 57 52 40 34 DIURNAL RANGE 27 24 27 27 19 14 12 13 16 18 24 26 RAIN/INCHES 1.2 1.4 1.8 1.4 4.2 5.4 6.1 5.7 3.9 3.9 1.1 0.3 HUMIDITY/% 65 66 61 60 68 75 82 83 79 79 72 71 BLOOM SEASON * * * * DAYS CLR @ 7AM 23 15 17 14 9 3 1 1 5 7 19 20 DAYS CLR @ 1PM 19 9 13 6 3 0 0 1 2 5 16 19 RAIN/MM 30 36 46 36 107 137 155 145 99 99 28 8 C AVG MAX 15.0 15.6 19.4 22.8 23.3 24.0 23.4 23.3 22.8 21.1 17.8 15.6 C AVG MIN 0.0 2.1 4.3 7.6 12.6 16.0 16.5 16.0 13.7 11.0 4.3 1.0 DIURNAL RANGE 15.0 13.5 15.1 15.2 10.7 8.0 6.9 7.3 9.1 10.1 13.5 14.6 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN
LIGHT: 1800-2500 fc. P. armeniacum is healthiest in rather bright, diffused light. It should not be exposed to direct sun. Strong air movement should be provided at all times, and plants thrive when placed in the strong, cool, moist airflow near the outlet of an evaporative cooler.
TEMPERATURES: Summer days average 75-75°F (23-24°C), and nights average 61-62°F (16-17°C), with a diurnal range of 12-14°F (7-8°C).
Winter days average 59-60°F (15-16°C), and nights average 32-36°F (0-2°C), with a diurnal range of 24-27°F (14-15°C). The increase in the diurnal range results from the somewhat cooler days and the much cooler nights.
HUMIDITY: 80-85% in summer and early autumn, dropping to 60-65% in winter and early spring.
WATER: Rainfall is moderate to heavy from late spring into autumn, with a 5-6 month dry season from late autumn to early spring. Although rainfall is low in early winter, moisture is also available from heavy dew, fog, and mist which is not indicated in the rainfall averages. Cultivated plants should be kept evenly moist while actively growing with only slight drying allowed between waterings. Water should be gradually reduced in late autumn, but plants should never be allowed to dry out completely.
FERTILIZER: A balanced fertilizer mixed at 1/4-1/2 recommended strength should be applied weekly to biweekly while plants are actively growing. Many growers recommend using a fertilizer higher in nitrogen, such as 30-10-10, if plants are potted in bark. Also, some growers recommend using a fertilizer lower in nitrogen and higher in phosphorus in autumn to promote better blooming the next season and to allow new growths to harden before winter. Fertilizer should be reduced or eliminated during the rest period until water is increased in spring.
P. armeniacum does not grow well when salts accumulate in the medium. In order to prevent salt buildup, the medium should be leached every few weeks when fertilizer is being applied. This is especially important in areas with heavily mineralized water. To leach the medium, first water the plant normally to dissolve any accumulated salts, and then an hour or so later flush the media with water equal to about twice the volume of the pot.
REST PERIOD: Growers report that cultivated plants grow and flower well with winter nights of 46-50°F (8-10°C), and some even indicate success with 60°F (16°C) nights. However, for the continued, long-term health of the plant, a cool winter rest should be provided. Plants that have evolved under conditions requiring a dormant or rest period sometimes suddenly expire for no apparent reason when they are allowed to grow continuously without a rest. They simply grow themselves to death. P. armeniacum probably does not need a rest period that is quite as long or severe as indicated by the climate table, but for at least 1-2 months, night temperatures should be lowered to near 50°F (10°C) and water should be reduced.
GROWING MEDIA: Plants may be somewhat difficult to manage because they tend to produce new growths as much as 6 inches (15 cm) away from the last growth. Because of the long rhizomes, new growths are easily trapped inside the pot which results in either damage or death of the new growth and possible disease in the mother plant. Consequently, many growers prefer to use a hanging basket made from wire mesh or wooden slats that is lined with moss. If pots are used, a wide, shallow type, such as a bulb pan, with a width about twice the depth is recommended. A regular pot which is large enough to accommodate the long distances between growths is too deep and stays wet too long. This quickly causes the medium to become soggy and stale, and conditions are then in place for a good case of root rot.
In nature, plants with long rhizomes often grow in thick moss or in deep layers of leaf humus suggesting that they are best cultivated in an open, well drained media that remains moist but not soggy. Most growers use fine or medium grade fir bark mixed with perlite or other moisture retaining additives. Chopped sphagnum is often added to the mix, especially in drier areas with low humidity. Charcoal may be included to keep the medium open and keep it from becoming sour. Because plants grow on limestone cliffs in nature, some growers recommend adding limestone chips to the medium. Growers are cautioned that limestone dissolves rapidly in cold water, however, and this may result in a buildup of toxic levels of calcium within the medium. Growers in areas with highly mineralized water should not add limestone to the potting mix.
Plants may be repotted at any time, but it is usually done in spring immediately after flowering. This gives the plant a chance to recover and become established before the stress of summer heat. When repotting, the junction of the roots and stem should be about one inch. (2.5 cm) below the top rim of the pot and about 1/2 in. (1.3 cm) below the top of the medium. If the medium settles so that the junction is exposed, more medium should be added to cover it.
MISCELLANEOUS NOTES: The bloom season shown in the climate table is based on cultivation records. Some writers, however, report blooming from summer through late autumn.
We hope that this information will provide
growers who have had trouble growing P. armeniacum with an
indication of what they might do to produce a healthy specimen. It is
indeed a beautiful plant. In our greenhouse, we have found it
relatively easy to grow and flower if minimal attention is given to
its cultural requirements.
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