The correct methods for repotting and watering orchids

Repotting

After an orchid has been in a pot for several years, the plant multiplies, the root system becomes overcrowded, affecting the growth and spreading of new shoots, and there is also rotting matter inside the pot, which provides favorable conditions for bacterial growth. Therefore, repotting, division, and replacing the potting medium are necessary.

Repotting generally refers to routine repotting, and according to the experience of our predecessors, the most suitable time is the early sprouting stage from the Spring Equinox to Qingming, or the early dormant stage from the Autumn Equinox to the Start of Winter. In addition, there is non-routine repotting, which can be carried out at any time as long as it is not during the two periods of high temperatures above 30 degrees or low temperatures below 5 degrees.

Before repotting, some preparatory work needs to be done, such as stopping watering for a few days to make the potting medium slightly dry and the roots slightly soft, which makes handling easier and can also prevent root breakage. Unused granular potting medium should be soaked in clean water for 3-5 days to let it become thoroughly wet; potting medium that is wet outside and dry inside is prone to problems. When using old potting medium and old flower pots for potting, strict disinfection is essential, and high-temperature treatment is the safest. Plastic pots cannot be treated at high temperature; disinfecting them with sunlight easily causes aging, so the most convenient method is to disinfect with a fungicide. Soaking in a 0.3 percent potassium permanganate solution for disinfection is fine, but white plastic pots will become stained with brown patches that are not easy to remove and affect their appearance, so a 500-fold diluted Thiophanate-methyl solution can be used instead for soaking.

After the plant is taken out of the pot, place it in clean water and brush off dirt with a brush. If you encounter granules tightly stuck together with new roots, do not forcibly brush them off, as doing it poorly may damage the roots. Then remove the rotting matter. Many books say to remove broken roots, hollow roots, old roots, and rotten roots. In my opinion, this cannot be generalized. A broken root is a break in the fleshy part, but its strand (central column) will not break, so it is enough to peel off the rotting part. Rotten roots often do not rot the strand; after peeling off the rotting part, examine the strand. If the strand is black, cut it off; if the strand is white, it still has the function of absorbing and transporting water and nutrients, and cutting it off is a great pity.

After cleaning, the next step is disinfection. Soak the plant in a 0.3 percent potassium permanganate solution or an 800-fold diluted Thiophanate-methyl solution for 30 minutes, then take it out and let it dry. I have used this method for disinfection and have seen no adverse consequences. Some people do not advocate washing and disinfecting, because doing so will remove and kill beneficial symbiotic bacteria, which is unfavorable for later growth. In my opinion, healthy home-grown plants can be left unwashed and undisinfected to protect the survival of symbiotic bacteria, but wild-collected plants, introduced seedlings, and diseased plants must be strictly washed and disinfected to eliminate hidden dangers.

When potting, for non-connected plant combinations, consideration should be given to the room for future development of new shoots and new roots, and they should not block the way forward; the arrangement of leaves should be well staggered and appropriately spaced. The potting medium in the pot is divided into three layers: upper, middle, and lower. Functionally speaking, the lower layer is the drainage layer, which should use coarser hard potting medium to facilitate drainage; the middle layer is the nutrient layer, and most orchid growers have their own formula, adding appropriate proportions of nutrient-rich substances such as humus soil, burnt mud ash, and human urine sediment; the upper layer is the protective layer, with finer potting medium. Some people plant Selaginella uncinata on it, and some cover it with sphagnum moss, all to protect the roots and keep it attractive and neat. After the drainage layer potting medium is added, the plant can be placed in. Hold the plant with one hand and add potting medium with the other. When the potting medium has been added to half the root height, gently lift the plant to an appropriate height so that the roots spread out. Then continue adding potting medium to the fixed height, pat the side of the pot a few times so that the potting medium and roots are closely combined, and finally add the protective layer potting medium. For plants with few roots, plastic strips should also be used to secure the plant to the flower pot so that it does not wobble, which helps survival.

After potting, water thoroughly once, commonly known as setting-root water. Some people advocate not watering immediately, because repotting and division inevitably create wounds, and watering affects wound healing. In fact, after the wounds are coated with slaked lime or sulfur powder, there is no longer much concern, and it is still better to water the setting-root water.

Watering

In addition to providing water to the orchid, watering also has the function of exchanging air among the potting medium. To achieve this purpose, the watering method also requires attention. Orchid-growing predecessors mostly used a fine-spouted long-necked pot to spray the orchid leaves and pot surface until water flowed out from the bottom of the pot. Watering in this way gives the potting medium a uniform water-receiving area. If a water ladle is used to pour water along one side of the pot rim, the water runs straight down along the pot rim (especially with coarse granular potting medium). Although water flows from the bottom of the pot, part of the potting medium is still dry, especially the potting medium in the center of the pot. Over time, this will inevitably cause part of the root system to dry out and endanger the plant's life. Urban orchid growers mostly use tap water, and because the water contains bleaching powder and chlorine, it needs to be stored for a few days before use. The leftover bottom water should be poured out, as it contains bleaching powder sediment.

Regarding orchid watering, our predecessors had a saying: "In spring it favors moistness, in summer and autumn it is slightly damp, and in winter it must be moist with a touch of dryness." The key words are moist and damp. How should these be understood? Dry and wet are the two extremes of potting medium; moist is the middle between dry and wet, that is, neither dry nor wet. The middle between damp and moist is wetter than moist and more moist than wet. Moist with a touch of dryness is the middle between moist and dry, drier than moist and more moist than dry. If this watering principle can be grasped well, then there will be no mistakes in watering.

Shen Yuanru's book "Orchids" has a section on watering, which is a summary of his lifetime of watering experience and is worth reading. A brief excerpt is as follows: after "Start of Spring," orchids begin normal growth, and the soil should be kept moist, sprayed with a fine-spouted long-necked pot once every four or five days. After "Awakening of Insects," root tips and bud points begin to stir, and daily watering should be frequent, but the amount of water should not be too much. After "Start of Summer," most orchids are in a semi-dormant state, and the pot soil should be slightly dry. From June onward, the weather gradually becomes hot, daughter plants grow quickly, and clean water is often sprayed on the leaves. After "Plum Season Begins," with continuous rain, air humidity is high, and watering should be controlled. After "Start of Heat," the weather is hot, and before sunrise every day, clean water is sprayed on the leaves and pot surface until the pot surface is soaked through. After "White Dew," the weather turns cool, and the amount of irrigation should be reduced, with watering only to the extent of moistening. After Mid-Autumn, the air is dry, and "water caltrop dryness" easily occurs, so water once in the morning and once in the evening. In late autumn, wash with water once every few days.

The reasoning of watering has been explained above, but whether the potting medium in the pot is dry or wet is still unknown. For tall plastic pots, I use the "toothpick detection method," which is simple and reliable, and it is worth trying. Take a strip of facial tissue (about 1 cm wide) and roll it diagonally around a toothpick. Insert it diagonally 2 cm into the ventilation hole of the plastic pot. After a moment, pull out the toothpick, and the degree of dryness or wetness of the facial tissue is the degree of dryness or wetness of the potting medium. If the upper hole is dry and the lower hole is wet, water less; if both the upper and lower holes are damp, do not water; if both the upper and lower holes are dry, water; if the upper hole is wet and the lower hole is dry, it is an incomplete "half-way" watering that did not penetrate, and the pot-soaking method should immediately be used to moisten the dry potting medium, and future watering methods should be improved.