Ecological Environment Requirements and Artificial Regulation Methods for Cymbidium

Large-floweredCymbidiumWhether its growth and development proceed normally is closely tied to the ecological environment in which it grows. Therefore, to grow and cultivate large-floweredCymbidiumwell, one must first carefully understand its growth characteristics and what kind of ecological environment meets its requirements, then according to the large-floweredCymbidium's growth characteristics and phenological stages, strive to select a superior natural ecological environment for cultivating the plants well or artificially create the conditions. To cultivate large-flowered Cymbidium well, one must choose a natural environment or one that has been artificially regulated to create the environment needed for the plants' growth. This is the key issue determining whether one can successfully grow and cultivate large-flowered Cymbidium. Large-flowered Cymbidium originally grew as a terrestrial or semi-terrestrial orchid in the high mountain valleys of Southeast Asia. Through long-term growth in this ecological environment, it has developed a preference for warm, highly humid, well-lit, well-ventilated, fresh-air conditions with a day-night temperature difference. Finding an ecological environment that meets these requirements is not always possible even in high mountain areas, let alone in plain regions where it is even more difficult. Therefore, while selecting a basic environment, artificial regulation is also essential to achieve the optimal ecological environment. Below, we summarize and describe our experience from long-term practice: I. Light Light mainly refers to sunlight, but also includes artificial light. It is the driving force for chlorophyll in the orchid plant to carry out photosynthesis. Without light, chlorophyll cannot perform photosynthesis, and thus cannot provide the necessary nutrients for the orchid plant. Differentorchidshave different light requirements, and even the same species oforchidhas different needs at various stages of growth and development. Large-flowered Cymbidium generally requires light levels of 15000 Lux to 70000 Lux, so it can be considered a light-loving plant. When the light level optimally meets the plant's needs, the plant grows robustly and upright, with short and wide leaves, thicker leaf texture, light green or yellow-green leaf color, plump and full pseudobulbs, a very high flowering rate, numerous flowers, and bright, glossy flower colors. Some people believe that the flowering rate is directly proportional to the amount of light, but this is not entirely correct, because more light is not always better; there must be a certain limit. If it exceeds 70000 Lux, photosynthesis actually slows down. Especially in summer and autumn, when temperatures are high, direct sunlight on the orchid leaves for extended periods will scorch them, producing what we call "sunburn disease." Therefore, in summer and autumn, direct sunlight must be artificially prevented to reduce light levels. Methods employed: on one hand, use shade nets of different specifications to regulate and reduce light levels; on the other hand, increase ventilation and humidity, otherwise the plants will inevitably be harmed. When light is below 10000 Lux, that is, insufficient light, photosynthesis is reduced, nutrition is inadequate, and in such an environment the orchid plant will grow leggy, with thin and long leaves, dark green leaf color, thin and soft leaf texture, and the whole plant will be weak and drooping, lacking vitality. Such plants have a very low flowering rate, and even when they doflower, they produce very few blooms, with dull, lusterless flower colors. Therefore, under insufficient light conditions, especially in winter and spring, the shade nets should be removed to allow as much light as possible into the orchid house. During prolonged rainy seasons, fluorescent lamps can also be used when necessary to supplement insufficient light. II. Temperature From over a decade of temperature observations in Xiamen, large-flowered Cymbidium has relatively strong temperature adaptability. In winter, no frost damage was found at low temperatures below 8°C. During short periods below 0°C, some varieties of seedlings in clustered seedling pots suffered frost damage, but no frost damage was found in medium and large seedlings or mature plants. In summer and autumn, sometimes high temperatures reach 38°C, and no abnormalities were found in the plants, but early flower buds and flower spikes cannot withstand the effects of high temperatures and will abort. Therefore, regarding temperature adaptability for large-flowered Cymbidium in Xiamen, the main issue is not increasing temperature but effectively cooling at certain stages. The optimal temperature for large-flowered Cymbidium is 8°C to 20°C at night and 20°C to 30°C during the day. Especially for three-year-old mature plants, June marks the beginning of flower bud differentiation. The day-night temperature difference must be regulated to 15°C to 10°C, so that flower bud differentiation through flower spike formation can proceed smoothly. Therefore, during this period we must adopt cooling measures. One approach is to move plantsthat willflower in late May to a natural ecological environment in a cool high mountain area at an altitude of about 1 km to force flowering, promoting flower bud differentiation and flower spike formation. By December, when temperatures in the plain areas have dropped and the day-night temperature difference is pronounced, the plants are gradually transported back for management and supplied to the market for sale. Another approach is not to go up the mountain but to move them into a protected orchid house, inputting cold air every night to control the temperature at around 20°C, and restoring daytime temperatures during the day, using artificial regulation to achieve the required day-night temperature difference. The former has low cost but requires more labor; the latter has high cost but saves labor. III. Humidity Large-flowered Cymbidium originated in the ecological environment of high mountain valleys, which has developed its relatively high humidity requirements. Beginners inorchid cultivationoften one-sidedly interpret humidity as the frequency of watering the growing medium in the pot, which is wrong. The humidity we refer to includes two aspects: the water-holding capacity of the growing medium inside the pot and the relative humidity of the air outside the pot. The growing medium in the pot should maintain a certain amount of moisture but must not become waterlogged. The growing medium must be kept well-aerated. If too much water accumulates in the pot, it will inevitably cause poor aeration, causing orchid roots to be soaked in water and to suffocate and die from lack of oxygen. If the medium in the pot is too dry, the roots have no water to absorb while the orchid leaves continue to transpire, inevitably causing the whole plant to dehydrate and die. Therefore, watering in the pot must first be based on the nature of the pot and growing medium, size and coarseness, different seasons, temperature levels, and various stages of plant growth and development (it is best thatorchidsplaced in the same orchid house be uniform), carefully considering when to water, how much to water, and how to water. This is a relatively complex and difficult-to-master issue inorchid cultivation. Humidity outside the pot refers to the relative humidity of the air in the orchid house. Large-flowered Cymbidium requires an optimal relative air humidity of 80% to 90%. To achieve such humidity in the growing area, artificial regulation must be relied upon. For example, in autumn and winter when the air is particularly dry, it is unfavorable for the growth and development of large-flowered Cymbidium, so during this season the air humidity needs to be increased. We can use humidifiers for automatic regulated misting, or we can use a simple method: when building the orchid house, first consider digging a water collection pool under the orchid bench of the same size as the bench, laying coarse sand or gravel at the bottom of the pool. During dry seasons, water can be introduced into the pool, so that the orchid plants are effectively placed above the pool. Due to the large evaporation surface, the air humidity in the orchid house can be maintained at the level needed fororchidplants. If the humidity still cannot reach the standard, additional water can be sprayed on the benches and walkways. This simple method has low cost and can also achieve the ideal relative humidity. In spring and summer, when there is more rain and temperatures are high, the relative humidity in the orchid house air sometimes exceeds 95% or even reaches saturation. This impedes transpiration of the orchid plants; the water absorbed by the roots cannot be consumed, which inevitably disrupts the plant's metabolism. In such cases, humidity must be promptly reduced artificially. The methods adopted are: stop misting, drain the water from the pool under the benches, open the doors, windows or surrounding barriers of the orchid house, and use electric fans or exhaust fans, suction fans and other machinery to increase air circulation in the orchid house, expelling the humidity so that the humidity in the orchid house will come down. By regulating according to different seasons in this way, the orchid plants in the orchid house can maintain optimal humidity at each different stage, allowing the plants to grow healthily. IV. Ventilation An idealorchid growingsite, in addition to attention to the selection and regulation of light, temperature and humidity, also requires attention to ventilation and fresh air. Because with good ventilation and fresh air,pests and diseasesand physiological disorders are reduced. Large-flowered Cymbidium requires gentle breezes throughout its entire growth and development process, generally judged by being able to see the tips of the plant's leaves swaying. This allows the water vapor evaporated from the leaves and polluted gases to be immediately blown away by the gentle breeze, which promotes the smooth circulation of root water absorption and leaf transpiration, enabling rapid plant growth. Especially from June to August each year, when light is intense, temperatures are high, and humidity is great, the orchid house often becomes stuffy and hot, with water vapor stagnating and not dispersing. This is a major taboo for orchids. It not only disrupts the plant's metabolism but also promotes the occurrence ofpests and diseasesand their rapid spread into disaster. Dust in the air also affects the plant's respiration and photosynthesis, hindering its growth and development. Therefore, air must continuously circulate and exchange for fresh air. At the same time, attention must be paid to the fact that air circulation also has limits and must be regulated according to the season. For example, too much circulation will inevitably damage the orchid leaves. In winter, when outside temperatures are low, cold air entering the orchid house is unfavorable for plant growth, so consideration should be given to reducing or stopping it, or timing ventilation at noon. The four environmental factors described above -- light, temperature, humidity, and ventilation -- are not isolated; they promote and constrain each other. Therefore, when we adopt artificial regulation of various factors to compensate for the deficiencies of the natural ecological environment, we must pay attention to different seasons and different growth stages, incorporating all four factors simultaneously into the scope of regulation and application, applying them flexibly to maintain the optimal ecological environment. (Wu Lianxing)