Key Environmental Control Techniques for Greenhouse Lily Cultivation

Lily cultivation, besides requiring high-quality bulbs, also requires strict control of the growing environment throughout the entire growth process according to the requirements of different varieties, in order to produce lily products with better plant form and higher quality. If conditions are not well controlled, it will not only affect the plant form of lilies, but in severe cases also affect plant growth, and may even prevent normal flowering. Below is a brief introduction to environmental control during greenhouse lily cultivation based on lily planting requirements.

Greenhouse selection: A good growing environment can ensure normal growth of lilies. Dutch lily cultivation generally has suitable greenhouses, and is equipped with various facilities capable of maintaining the greenhouse under suitable climatic conditions (light, temperature, ventilation, air circulation). In domestic lily cultivation, due to differences in climatic conditions and cultivation levels across regions, greenhouses are also diverse, such as plastic tunnels or multi-span greenhouses, and in many places lilies can also be planted directly in the open field when the climate is suitable. Each region should choose flexibly according to climatic and economic conditions, but if cooling or shading is needed in summer, or cooling or supplemental lighting is needed in winter, then caution should be taken, and at least basic heating or cooling facilities and suitable irrigation facilities are required.

Temperature: To obtain high-quality products, cultivating a good root system is very important. During the first 1/3 of the growth cycle, or at least before stem roots emerge, the suitable temperature is 12°C-13°C, which is beneficial for the growth of lily stem roots. Too low a temperature will prolong the growth cycle, while a temperature above 15°C will lead to poor rooting and reduced product quality. After that, the temperature gradually increases, and for different lily strains, the suitable growth temperature also differs; see the attached table for details.

High temperature and drought will cause lily stems to become shorter and the number of flower buds to decrease; high temperature and high humidity will cause lily stems to become soft and not firm, and leaves to become thinner; low temperature will delay plant growth and prolong the growth period; rapid changes in temperature and humidity will produce aborted flower buds and increase the rate of split buds and scorched leaves, so the entire process of lily cultivation requires maintaining suitable temperature and humidity, with gentle changes. Ventilation can reduce temperature and humidity under high-temperature and high-humidity conditions, making plants grow robustly and reducing pests and diseases. In winter or in cold regions, heating systems are usually used to control the temperature of greenhouses or plastic tunnels. There are many heating methods, such as oil (coal) hot air blowers, hot water pipe heating, steam pipe heating, etc. The power of the heating system needs to be about 220 watts per cubic meter per hour, and each region should choose according to specific circumstances.

Using hot water pipe heating gives a more uniform heat distribution and good operational safety, but pipe heating often raises the temperature relatively slowly. Using an oil-fired hot air furnace for heating is more convenient, but it must be ensured that the heat distribution of the system can be uniform. In addition, there must be a suitable outlet so that the combustion gases can be discharged freely. If combustion gases accumulate in the greenhouse, both ethylene and nitric oxide gases will cause lily bud drop or poor growth. Heating systems such as pipes or hoses (maximum temperature 40°C) can also be installed under the ground beds.

Ventilation and relative humidity: The suitable relative humidity for lily growth is 80%-85%. Relative humidity should avoid too much fluctuation, and changes should proceed slowly, otherwise it will cause stress and scorch the leaves of sensitive cultivars. Both temperature and relative humidity can be regulated using measures such as ventilation, air exchange, shading, watering, and heating, and the two often change simultaneously. Under mild, low-light, windless, and humid climatic conditions, relative humidity is usually very high, and ventilation must be strengthened to reduce relative humidity. In winter, ventilation is best carried out in the morning when outdoor relative humidity is relatively high. Full attention must be paid to the importance of ventilation in summer. Experiments show that in regions with little rain, lilies planted in the open field in summer have better stem and flower bud quality than those planted in greenhouses with poor ventilation and excessive shading. But note: when it rains, it is best to temporarily cover with film to block rain, so as to prevent rainwater from damaging lily stems, leaves, and flower buds. If summer temperatures are very high, a wet pad ventilation system can also be equipped to improve the environment inside the greenhouse, but this investment is relatively large. Install a special paper wet pad with a thickness of 10-15 cm on the north-facing wall of the greenhouse, and install a high-power exhaust fan on the corresponding greenhouse wall. When in use, the entire greenhouse must be closed, the wet pad water pump turned on to fill the entire wet pad with water, and then the exhaust fan turned on to discharge the air inside the greenhouse and draw in outside air. When the hot outside air passes through the wet pad, the evaporation of water lowers the temperature of the air entering the greenhouse, thereby achieving the purpose of lowering the temperature inside the greenhouse. Note: the length of a greenhouse using wet pad ventilation cooling should be strictly controlled at about 40 m; the effect of using wet pad ventilation cooling in regions with low air humidity is better than in regions with high air humidity. A micro-mist system can also be used for cooling, but due to excessively high humidity, the cooling effect is often unsatisfactory. Therefore, in regions with high humidity and high temperature, the more feasible method for cooling and reducing humidity can only be to strengthen ventilation together with appropriate shading, which can reduce the temperature and humidity on the leaf surface and make plants grow robustly. To ensure smooth ventilation around the greenhouse, the height of the skirt should be increased as much as possible to strengthen ventilation.

Light: Asiatic lilies are very sensitive to insufficient light, but there is great variation among varieties. Lilium longiflorum is less sensitive than Asiatic lilies, and Oriental lilies are the least sensitive. Light directly affects the growth, development, and flowering of lilies. When light is insufficient, plants will grow poorly due to a lack of sufficient organic matter, with thin and soft stems, thin leaves, stems and leaves bending toward the light, and thin, pale flower buds; in severe cases, it will also cause bud drop and shorten vase life. When light is too strong, it can also inhibit plant photosynthesis. Light also raises the medium temperature, which accelerates plant growth and stem elongation. Light regulation can be carried out through methods such as shading in summer and supplemental lighting in winter. When planting lilies in East China, supplemental lighting is usually not needed; when cultivating in winter in northern regions, if light is insufficient, consider installing one 400-watt sun lamp with a dedicated reflective surface per 10 sq m for supplemental lighting. Moreover, it is best to choose varieties that are not very sensitive to light, and plant the bulbs more sparsely.

When summer temperatures are too high and light is too strong, shading is needed to avoid harm to plant growth caused by high temperature and strong light. Shading directly affects the temperature, humidity, and light conditions inside the greenhouse. In months with high light intensity, the temperature inside the greenhouse may rise rapidly. In this case, appropriate shading is necessary. Especially in the first three weeks after bulbs are just planted, more light needs to be blocked. But be careful to prevent excessive shading, because excessive shading will lead to insufficient light. Shading can use shade nets; abroad, the method of brushing white ash on film is also used, but it is not commonly used domestically.

Carbon dioxide gas: The carbon dioxide content in air is generally around 300 ppm. If the carbon dioxide concentration in the greenhouse can be increased to around 1000 ppm, it can significantly promote lily growth, making plants stronger and greener, with a lower probability of bud drop.