Genus Oncidium Sw. - One of the most numerous genera of orchids, numbering more than 700 species. The birthplace of oncidiums is Central and South America, some species are found in southern Florida. Most of the plants are epiphytes with oval, oblate bulbs, bearing one or two apical leaves. Leaves are often leathery, lanceolate. In some species, bulbs are reduced. The sizes of plants vary greatly - from a few centimeters to half a meter. The peduncle of many species is long, branching, with a large number of flowers. The flowers are medium-sized; yellow and brown colors predominate. The roots of oncidiums form a thick drooping "beard" in which humus accumulates.
Oncidiums are plants with distinct periods of growth and dormancy. The exception is heat-loving species.
Many species can be grown indoors under not very high light conditions. They grow well and bloom when kept for most of the year under fluorescent lamps.
Heat-loving species (O. lanceanum, O. papilio, O. kramerianum, O. splendidum, O. nanum, O. tigrinum, O. sanderae, O. pusillum, and some others) require higher illumination. They are shaded from direct sunlight at noon during growth (should not be shaded in autumn). In winter, it can be kept at a temperature of 18–20 ° С.
Medium-temperature species originating from elevated places (O. sphacelatum, O. forbesii, O. luridum, etc.) tolerate lower winter temperatures well - up to 12-15 ° С. High temperatures are poorly tolerated by O. flexuosum, O. crispum, O. ornithorhynchum, O. carthagenense, O. macranthum.
A humidity of 40-60% is sufficient for the maintenance of oncidiums. Like all other orchids, they respond well to increased humidity during the growth period. At rest, watering is greatly reduced. Species with large bulbs easily tolerate a long dry period. Heat-loving species watered all year round quite abundantly.
For planting oncidiums, various containers are used. Cold-loving species develop well on porous ceramic cylinders or segments of asbestos-cement pipes. With this planting, plant roots are cooled by evaporation of water from the surface of the cylinder.
When using an asbestos-cement pipe, one of its ends is clogged. The pipe is soaked for 2-3 weeks, regularly changing the water, after which the plant is attached, placing the roots on the outer surface of the pipe. Water is poured into the cylinder. In this way, O. crispum, O. enderianum, and some other species are successfully grown in Florida, where summer temperatures can rise to 40 ° C.
Conventional epiphytic substrates can be used. With frequent wetting, small species grow well on the bushes of the bark, stumps of branches. For fertilizer use solutions of mineral salts of conventional concentrations. Transplanted if necessary.
Numerous intra- and intergeneric hybrids of oncidiums with odontoglossums, miltonia, and others are successfully grown under indoor conditions. These hybrids in their decorative qualities are often significantly superior to the original wild-growing species. In addition, most of them are less demanding of the conditions of room culture. This explains their widespread popularity.
Characteristics of the most interesting species are given in table 10.
Table 10. Genus oncidium. Characteristics of species and habitats