Environmental factors of orchids: moisture

Most orchids are born in a rainy but well-drained environment, so they like to be moist and afraid of excessive water retention. However, different kinds of orchids have different requirements for water, so they should not be mixed together during cultivation. For example, compared with many hybrids of Magnolia, Cartland needs more sunlight, lower temperature and less water than the latter, so they cannot be placed in the same environment, or at least not on the same shelf. For example, using bark, pebbles and clay blocks as cultivation substrates evaporates much faster than using water moss, purple dustpan and foam as substrates. Orchids cultivated with different substrates cannot be put together. In this way, it can be watered in pieces according to the need, without confusion.

Rain Water, snow water and natural soft water (river water, well water) are the best water for orchids. But in heavily polluted cities, there will also be harmful substances in rain and snow. Try to avoid using hard water and artificially treated soft water, which (such as ion exchange resin) changes calcium in the water into sodium, which is more harmful to orchids than calcium. The frequency of watering varies with the season, which should be watered frequently in summer and strictly controlled in winter. Watering time can be done at any time of the day, except for the scorching at noon and the cold at night.

Generally, green plants absorb water during the day. At this time, the stomata open, absorb carbon dioxide, absorb solar light energy through chlorophyll, carry out photosynthesis, and synthesize carbon dioxide and water into organic compounds; at the same time, water is also lost due to transpiration. At night, through respiration, organic acids are decomposed into carbon dioxide and water with the participation of oxygen, producing energy for plant growth and releasing carbon dioxide and water. Most of the terrestrial orchids, including the national orchids, dipper orchids, and most of Paphiopedilum belong to this type. In other words, it absorbs water during the day and releases it at night. So watering plants when they absorb water during the day is best when the temperature begins to rise, especially in winter, and in summer after the sun rises. The main purpose of this is to prevent the difference between the water temperature and the temperature of the plant (mainly the root) so as to damage the absorption function of the root. Greenhouse orchids in the north should pay special attention to this. I'm afraid it may not be reasonable for Zhang Guolan to water some books sooner or later, or even at night.

It is worth noting that a considerable number of orchids, mainly epiphytic orchids with thick leaves, have the physiological characteristics of drought tolerance. Such as Cartland, Dendrobium, Phalaenopsis and so on all belong to this category. Because their methods of fixing carbon dioxide are similar to those of succulent plants of crassulaceae, they are called crassularic acid metabolism (Crassulacean Acid Metabolism), or CAM for short. Such orchids open their stomata at night because of the highest humidity in the air at night (nature), carbon dioxide is fixed and stored as malic acid, making the cell sap strongly acidic at night. During the day, carbon dioxide is released for photosynthesis. CAM metabolic type is an adaptation to xerophytic environment, because stomata are not opened during the day, water loss can be reduced, while humidity is high at night, and there is plenty of carbon dioxide in nature. But if there is enough water, the stomata can also open during the day to absorb carbon dioxide and carry out photosynthesis. For this kind of orchid, watering during the day and dusk is OK, as long as the water temperature is right.

The amount of watering is based on the wetting of the matrix. However, watering once a few days should be decided according to the species, substrate, cultivation environment and local climatic conditions of orchids. The most important thing is to rely on the grower to observe carefully and make a judgment in the light of reality. It is usually not possible to completely dry the matrix. When growing orchids with water moss or partially with water moss, if the water moss turns white, it shows that it is too dry; if you use bark, styrofoam and other substrates, although the appearance is dry, it may still be wet inside, so you should observe carefully.

In the north, it is difficult to use natural water to water orchids. On the other hand, tap water is often disinfected with bleach and is slightly alkaline. When you have to use tap water, it should be injected into the artificial pool and stored in reserve. As long as it is exposed to the sun for a long time, the chlorine will be lost and the bleach will precipitate. Because orchids mostly come from tropical and subtropical regions, where the pH of matrix and water is mostly pH5.2~6. If the pH of the water is too large (above pH7, that is, neutral or alkaline), it can be treated with hydrochloric acid, oxalic acid, acetic acid or citric acid to reduce it to pH 5.2-6. On the other hand, in some areas of the south, when the acidity of water is too large, it can also be treated with caustic soda, such as sodium hydroxide or potassium hydroxide.

The method of watering is also particular. Generally, it can be divided into water injection, spray and immersion. Water injection refers to injecting water directly into the matrix with a spout. Generally use a long-mouth kettle to prevent the kettle from touching orchid pots and orchids; water should be injected slowly to make sure the matrix is soaked. Do not use a large-diameter kettle or tap water pipe to avoid splashing soil, polluting leaves, or causing substrates such as bark to float out of the flowerpot, and will not cause the temperature of the substrate to rise and drop sharply. Shower sprinklers should be used for water spraying, and small hole sprinklers should be used for seedlings so as not to damage tender leaves and stems. In addition, we should also pay attention to the buds and flowers, so as not to let water into them and cause decay. Water spraying can alleviate and decrease the excessively high room temperature. Immersion is to put the flowerpot into the water, wet the matrix from the bottom up, to the degree of moisture, not too wet. In short, it should be suitable for orchids not only afraid of long drought but also avoid stagnant water, like moist but not wet, dry but not dry. (Chen Xinqi, Ji Zhanhe)