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ORCHID SPECIES CULTURE Charles and Margaret Baker Psychopsis versteegiana (Pulle) Lückel & Braem AKA: Oncidium versteegianum Pulle. ORIGIN/HABITAT: Peru, Surinam, Ecuador, and Bolivia. This species was originally discovered along the Tapanahoni River in Surinam but was never again found in that locality. Later collections in Surinam were made near the Curantyne River at King Frederick Williams Fall. In Bolivia, plants were found at 1500 ft. (450 m) on old citrus trees in wet forest regions near San Rafael in Chapare Province, which is in the northeastern section of the Department of Cochabamba. In Peru, plants have been found near Tingo Maria in the Department of Huanuco as well as in the Departments of San Martin and Pasco. They generally grow on trees in wet mountain forests at 1950-3950 ft. (600-1200 m). Habitat information for plants found in Ecuador is not available. Bennett and Christenson (1993) state that between 1961-1989 collections made in Ecuador, Peru, and Bolivia were mistakenly identified as Psychopsis sanderae Rolfe. CLIMATE: Station #84534, Tingo Maria, Peru, Lat. 9.1S , Long. 75.9W, at 2106 ft. (642 m). Temperatures are calculated for an elevation of 3950 ft. (1200 m), resulting in probable extremes of 91F (33C) and 33F (1C). N/HEMISPHERE JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC F AVG MAX 80 82 82 81 81 81 80 79 80 80 81 80 F AVG MIN 57 58 58 59 59 60 60 60 60 60 59 58 DIURNAL RANGE 23 24 24 22 22 21 20 19 20 20 22 22 RAIN/INCHES 5.8 8.2 8.0 15.9 24.9 12.0 15.9 16.4 22.8 8.5 8.7 4.5 HUMIDITY/% 78 76 77 79 78 80 81 81 81 80 78 79 BLOOM SEASON N/A DAYS CLR @ 7AM 2 3 3 1 1 1 0 0 0 1 1 1 DAYS CLR @ 1PM 15 12 9 3 4 4 4 1 4 2 7 12 RAIN/MM 147 208 203 404 632 305 404 417 579 216 221 114 C AVG MAX 26.7 27.8 27.8 27.2 27.2 27.4 26.7 26.1 26.7 26.7 27.2 26.7 C AVG MIN 13.9 14.4 14.4 15.0 15.0 15.5 15.5 15.5 15.5 15.5 15.0 14.4 DIURNAL RANGE 12.8 13.4 13.4 12.2 12.2 11.9 11.2 10.6 11.2 11.2 12.2 12.3 S/HEMISPHERE JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN Cultural Recommendations: LIGHT: 1800-2500 fc. Plants may tolerate even brighter light if high humidity and strong air movement are provided. TEMPERATURES: Throughout the year, days average 79-82F (26-28C), and nights average 57-60F (14-16C), with a diurnal range of 19-24F (11-13C). These temperatures represent the coolest conditions under which this species should be grown. Because of the especially large area of distribution and the wide range in habitat elevation, plants should adapt to conditions 4-6F (2-3C) warmer than indicated. HUMIDITY: 75-80 % year-round. WATER: Rainfall is very heavy throughout the year. However, other areas in the habitat are probably not as wet as the region around Tingo Maria. In some areas, there may even be a brief semi-dry period in autumn or winter. However, the common description of the habitat in all collection reports indicates heavy rainfall most of the year. Cultivated plants should be watered often, but the roots must dry rapidly after watering, and the medium should never get soggy or sour. FERTILIZER: A balanced fertilizer, mixed at 1/4-1/2 recommended strength may be applied weekly while the plant is actively growing. Many growers use a lower-nitrogen, higher-phosphate fertilizer starting in late summer and autumn. This helps promote better blooming the next season and slows new growth allowing it to harden before winter. REST PERIOD: Growing conditions should be at least as warm as indicated and should be maintained all year. Water may be reduced somewhat in winter, especially for plants growing in the dark, short-day conditions common in temperate latitudes, but they should not stay dry for long periods. If water is reduced, fertilizer should also be reduced until water is increased in spring. GROWING MEDIA: Plants may be mounted on tree-fern or cork slabs if humidity is high and plants are watered at least once daily in summer. Mounted plants may need several waterings a day during very hot, dry weather. Many growers have trouble keeping mounted plants moist enough, and they are prefer to grow their plants in shallow pots or baskets using an open, fast draining medium. The medium may contains materials that holds some moisture, such as chopped sphagnum or perlite, but it must dry fairly rapidly after watering. Charcoal is often added to help hold the medium open and keep it from turning sour. Undersized pots just large enough to hold the roots should be used. Repotting should be done only when necessary, and then only just as new root growth is starting. This is when the plant is best enable to become reestablished in the shortest possible time. Our plant grows well for us in a galvanized chicken-wire basket lined with coconut fiber and then filled with a mixture of fine- and medium-grade tree-fern fiber mixed with about 10% perlite and 10% charcoal. MISCELLANEOUS NOTES: These plants reportedly bloom sporadically throughout the year both in the wild and in cultivation. Plant and Flower Information: PLANT SIZE AND TYPE: A clump-forming, 7-14 in. (19-35 cm), sympodial epiphyte. PSEUDOBULB: 1.6-2.2 in. (4.0-5.5 cm) long by about as wide. The broadly ovate to suborbicular pseudobulbs are laterally flattened or compressed and irregularly wrinkled with rounded edges. The sheaths that partially cover the pseudobulbs are short-lived, thin, dry, and grow from the base. They are about 3 in. (7.5 cm) long by 0.9 in. (2.2 cm) wide. The exposed surfaces of each pseudobulb are dark reddish purple, but the protected area under the sheaths is green. LEAVES: 6-12 in. (15-30 cm) long. A single elliptic to oblong-elliptic leaf is carried at the top of each pseudobulb. The keeled, more or less sharply pointed blade is 1.6-3.5 in. (4-9 cm) wide and tapers to a short, folded petiole at the base. The upper surface of each leaf is a dull olive-green that may be mottled with an faint pale green if grown in low light or a more conspicuous red-purple when grown in brighter light. The underside of each leaf is red-purple mottled with green. INFLORESCENCE: 26-43 in. (65-110 cm) long. The erect, flexuous flower scape emerges from the base of the newest growths. The base of the peduncle is broadly elliptic in cross section but gradually becomes flatter so that the tip is sufficiently flattened that it has 2 relatively sharp edges. Each internode is 2.6-4.0 in. (6.5-10.0 cm) long. The thin, dry bracts at the base are about 1 in. (2.5 cm) long, but they are shorter on the upper nodes. FLOWERS: 1 at a time, 3-5 per inflorescence. Blossoms develop one at a time, on each inflorescence. Flower spikes should not be cut when flowering is finished because after the terminal bud dies, lateral branches often develop, thereby producing another series of flowers. The large, showy flowers are up to 4.5 in. (11.4 cm) long by 2.2 in. (6 cm) wide. The erect very narrow, petals and dorsal sepal are 2.5-2.8 in. (6.2-7.0 cm) long by only 0.3 in. (0.7-0.9 cm) wide. They are greenish yellow with dark reddish brown markings on the lower half and usually a solid reddish brown on the upper half, but sometimes the upper half of these segments is partly yellow along the margins. The wide-spreading, sickle-shaped lateral sepals are very different. They are 2.0-2.2 in. (5.0-5.6 cm) long by 0.8-0.9 in. (2.0-2.3 cm) wide with lightly crisped-undulate margins. They are bright yellow or greenish yellow heavily marked with brownish orange transverse bars or blotches. The 3-lobed, fiddle-shaped lip is 2.0-2.4.in. (5-6 cm) long overall, and the wide-spreading midlobe is about 1.6 in. (4 cm) long by almost 2 in. (5 cm) wide. The lip is bright yellow with a variable amount of brownish orange on the sidelobes and on the margin of the midlobe. These brownish orange markings may vary from light blotching to solid, and the amount on the margin of the midlobe may vary from a wide, irregular band to a narrow one. The margin of the midlobe, which is very wavy, is deeply notched at the apex. The elongated callus, which is pale yellowish white with pale brown markings, lies between the lateral lobes and extends a little past their center. It has 2 thick, keeled ridges that are separated by a stout, subcylindrical, bluntly tipped center section. The stout column is green and red-brown with a pale cream anther. The flattened wing on each side of the column has narrow, comblike, parallel projections with the lowest tooth or division is elliptic in shape and much broader. HYBRIDIZING NOTES: Chromosome count is 2n = 38. REFERENCES: Bennett, D. E. Jr. and E. Christenson. 1993. Icones Orchidacearum Peruviarum. Pub. privately by A. Pastorelli de Bennett. Braem, G. J. 1993. Studies in the Oncidiinae. Schlechteriana 4(1-2):8-29. Dodson, C., and R. Vásquez Ch. 1982. Orchids of Bolivia, Fasc. 6, plates 501-600. Icones Plantarium Tropicarum . Marie Selby Botanical Gardens, Sarasota, Fla. Kennedy, G. 1977. The section Glanduligera of the genus Oncidium. Orchid Digest 41(4):139-141. Rolando, I. and E. Christenson. 1993. Peruvian Orchids. The rediscovery of Psychopsis sanderae (Rolfe) Lückel & Braem and elucidation of Psychopsis versteegianum (Pulle) Lückel & Braem. Orchid Digest 57(3):116-118. Schweinfurth, C. 1958-1961. Orchids of Peru. Fieldiana: Botany 30(1-4). Chicago Natural History Museum Press, Chicago. Copyright 2000, Charles O. Baker and Margaret L. Baker Sheet version 94436923 ......................................................................... 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