Environmental factors of orchids: ventilation

Orchids are mostly ventilated on four sides in the natural environment. Epiphytic orchids are also called aerial orchids, and even their roots are exposed to the air. Terrestrial orchids are mostly born in places full of humus and gravel, and the air is also ventilated. District Jinze said in "Linghai Lanyan": "ventilation is the priority of orchids." He also said: "Langui is ventilated, covered and kept secret." This is his experience of growing orchids. This is especially true in the north. Because growing orchids in the greenhouse has affected ventilation, if it is sheltered again, the impact will be even greater, often resulting in adverse consequences. The main purpose of ventilation is to supply fresh air to orchids. Carbon dioxide and other free ingredients in the air are necessary for orchid metabolism. Stomata distributed on the lower surface of the leaves absorb carbon dioxide and other nutrients contained in the air. The roots of some epiphytic orchids, such as Phalaenopsis, Cartland, Wandailan and so on, can also absorb nutrients from the air. Therefore, constantly changing the air is very important for the growth of orchids. At the same time, ventilation can also remove dirty air, including harmful gases, regulate and lower the temperature, and inhibit the growth and spread of diseases and insect pests. In addition, carbon dioxide is heavier than air, and a breeze is needed to make it flow so that it can come into contact with orchid leaves throughout the greenhouse.

There are two aspects of ventilation to be done. The first is to keep the orchid itself ventilated, including the ventilation of the matrix around the roots and the ventilation between the orchid plants; the second is the ventilation of the greenhouse where orchids are cultivated. However, when growing orchids in the open air in the south, there is generally no ventilation problem, unless the whole orchid farm is chosen in a sultry, unventilated depression.

Greenhouse ventilation is mainly with exhaust fans, supplemented by window ventilation. Even in the most developed countries, there are not air-conditioned orchid greenhouses everywhere. As far as I know, most small and medium-sized orchid farms grow orchids in plastic sheds and simple greenhouses, and ventilation mainly depends on exhaust fans. Exhaust fans have different powers, there are fans close to the roof, but also close to the ground, but do not blow to the orchid, but to the horizontal direction, the effect is very good. In particular, the roof fan can quickly blow away the hot air to prevent the room temperature from being too high. The main taboo of ventilation is to prevent the introduction of too much dry air from the outside, resulting in a decrease in greenhouse humidity, or a sharp change in indoor temperature due to the large temperature difference between indoor and outdoor, thus affecting the growth of orchids. Therefore, the growers should adjust reasonably according to the local temperature, humidity and other climatic conditions, as well as the species of orchids. (Chen Xinqi, Ji Zhanhe)