Detailed Explanation of Orchid Environmental Factors: The Effect of Light on Orchid Growth

Light, temperature and humidity are ranked together as theorchidthree major factors for growth. Its influence onorchidgrowth and development is very important. Mostorchidsgrow in natural environments that have both sunlight and shade, such as on isolated trees, at forest edges, in bright openings within forests, and on rock faces with diffused light. However, different orchids have different requirements for light duration and intensity. Like other plants, orchids can also be divided into long-day orchids and short-day orchids. Long-day orchids bloom as the days gradually lengthen and the nights gradually shorten; short-day orchids are the opposite, blooming as the days gradually shorten and the nights gradually lengthen. The former mainly bloom in late spring and summer, while the latter bloom in late autumn and winter. There is also a third category, intermediate orchids between long-day and short-day types. Such orchids have the physiological readiness to bloom at any time and are more adaptable to changing environments, and their flowering period is usually not strictly limited to a particular time. Generally, short-day type orchids can be brought into bloom with 8-9 hours of sunlight per day, while long-day type orchids need 12-14 hours of sunlight to bloom. Besides the duration of light, the intensity of sunlight also has an effect. People often regulate light duration and light quantity to advance or delay flowering time. Of course, this is a rather complex issue, and it also involves the mutual influence of factors such as temperature and humidity; a thorough understanding of the ecological environment of the orchids' places of origin is needed in order to better carry out artificial regulation in combination with specific conditions. TheThe floweringphysiological preparation gives the plant greater adaptability to environmental changes, and the flowering period is usually not strictly limited to a particular time. Generally, short-day orchids can be brought into bloom with 8-9 hours of sunlight per day, while long-day orchids need 12-14 hours of sunlight per day to bloom. Besides the length of light exposure, the intensity of sunlight also has an effect. People often regulate the duration and amount of light to advance or delay the flowering time. Of course, this is a rather complex issue, and it also involves the mutual influence of factors such as temperature and humidity; a deep understanding of the ecological environment of the orchid's place of origin is needed in order to better carry out artificial regulation in combination with specific conditions. Lanorchid'slight requirement also varies with species. Even the same species differs at different growth stages and in different seasons. But in terms of overall light requirement, they can be roughly divided into three categories: sun-loving, semi-shade-loving and shade-loving. Sun-loving types basically need no shading or only very slight shading; semi-shade-loving types need 50%-70% shading; and shade-loving types need 70%-90% shading. This is only a rough distinction, with no absolute boundaries. Each category can be further subdivided. Generally speaking, species that are deciduous in the dry season or in winter need more light than evergreen species; epiphytic species need more than terrestrial species; small-leaved species need more than large-leaved species; thick-leaved species need more than thin-leaved species. This is a general conclusion drawn from extensive analysis of the ecological environments of orchids' places of origin. But this is not absolute; even the same species differs in different regions and at different altitudes. Taking native Chinese orchids as an example, Spiranthes sinensis and some Epipactis species are sun-loving and basically need no shading; Thunia alba, Arundina graminifolia and some Cypripedium species need only 30%-40% shading; some species of Vanda, Dendrobium and Oberonia need 50%-60% shading; some species of Coelogyne need 60%-70% shading; Chinese orchids are generally shade-loving, with most species needing 70%-85% shading; and most species of Calanthe need 85%-90% shading. This is a rough estimate, and in fact within the same genus the light requirements can sometimes differ greatly. For example, Paphiopedilum insigne is semi-shade-loving, while Paphiopedilum villosum is shade-loving; Dendrobium fimbriatum is semi-shade-loving, while Dendrobium henryi is shade-loving. Among the familiar Chinese orchids, the situation is also different.Cymbidium ensifoliumis relatively light-loving, with a shade level of about 60%-70%;Cymbidium goeringiineeds a somewhat greater shade level, about 70%-80%;Cymbidium sinenseneeds a shade level of up to 85%. In addition, shading also has a certain relationship with season, time of day and temperature. For example, more shading in summer and less in winter; more shading at noon and less in the morning and evening; more shading at high temperatures and less when cool; more shading at low altitudes and less at high altitudes, and so on. Regulating light is extremely important to orchid growth and development. Usually people can judge whether the light intensity is appropriate by carefully observing the orchid's growth. For example, if the leaf color turns light green, it indicates that the light is too strong; if it becomes yellowish-white or even scorched and withered, it indicates that the light intensity has exceeded the level the plant can tolerate. Conversely, if the leaf color is dark green or deep green and lacks luster, it indicates that the light is too weak. On the other hand, the plant's growth and flowering can also be used to judge. If light is insufficient, the plant grows weakly, with many leaf buds and few flower buds, and the number offlowersis small and the colors are not bright; if light is too strong, there are few leaf buds and many flower buds, and growth is also abnormal. Regulating light mainly relies on shading, that is, weakening the light rather than completely blocking it. This is because most orchids in nature grow in shady environments with scattered sunlight, and semi-shade-loving and shade-loving types account for more than 4/5 of all orchid species. Therefore, imitating the natural environment and using plants for shading is one of the relatively ideal methods. Some orchid nurseries in the south plant trees and vines as partial shade frames, and in the north various plants are grown around greenhouses for summer shading; both are very good approaches. However, plants cannot be moved freely and have their limitations, so it is also very necessary to use other artificial shading devices at the same time. In recent years, the most widely used is shade netting, which is light, durable, and available in specifications with different shading densities. Others such as bamboo blinds, reed blinds, straw blinds and colored plastic panels can also be chosen according to actual conditions. (Chen Xinqi, Ji Zhanhe)