How to rescue a white orchid (Michelia alba) that is dropping its leaves? A few practical methods

Mr. Jiang Hongyou, Room 301, No. 24 Duanzhuang, Huaihai West Road, Xuzhou City, Jiangsu Province, wrote in to ask: In spring I bought a batch of whiteorchidflowers from the south. They grew luxuriantly in summer and autumn. At the end of October they were moved into a greenhouse. When the temperature dropped to -2°C to 3°C, I began heating with a coal stove, about 25°C to 30°C during the day and above 10°C at night. On December 15 I watered once with 12°C cold water. On the night of the 17th the smoke pipe burst and they suffered smoke damage once. After the 20th the white orchids dropped a large number of leaves, and 5 days later the leaves of several hundred pots of white orchids had almost all fallen off. May I ask: What caused the white orchids to drop so many leaves? Is there any danger after the leaves fall? Answer: The main reason your white orchids dropped so many leaves was the smoke that leaked into the greenhouse when the smoke pipe burst at night. The exhaust gas produced by burning coal contains some toxic substances, such as sulfur dioxide, carbon monoxide and some nitrogen oxides, hydrocarbons, etc., as well as a relatively large amount of COD, exceeding the limit that white orchids can tolerate, and white orchids happen to be especially sensitive to smoke damage, which inevitably caused them to drop a large number of leaves in a short time; secondly, there may also have been factors such as low temperature and poor ventilation, or suddenly watering heavily after the potting soil had become too dry, but the latter is not very likely. If your white orchids have only lost their leaves, the young branches are not too greatly affected, and the terminal buds are still intact and alive, you can take 1 to 2 whiteorchidplants out of the pots and check whether their root systems have died from suffocation. If the buds are alive, the branches are still green, and the roots are intact, generally there will not be too great an effect on the next year's growth, and at least there will be no danger of death. Measures to take for rescue: First, a proper double-layer plastic greenhouse should be built, covered with straw curtains or black netting, and the temperature inside must be kept no lower than 0°C to 5°C, with the day-night temperature difference not exceeding 5°C to 8°C; if heating is necessary, electric heaters, electric heating panels, electric stoves, etc. can be used. If a coal stove really must be used for heating, the pollution from exhaust gas produced by burning coal must be effectively eliminated, otherwise it will only make things worse. Second, at noon when the weather turns warm, appropriately open the door openings for ventilation; the air inside the greenhouse must be kept fresh, but cold wind must also be prevented from blowing in. Third, the potting soil is best kept moist, not too dry, and even more so not too wet, otherwise it is very easy to cause its fine, tender, fleshy fibrous roots to shrivel and die or to rot and die; watering can be changed to misting, using a knapsack sprayer to mist the branches and trunks every day, and the water temperature must be basically the same as the temperature inside the greenhouse; a great difference must be avoided, so that they cannot bear it and suffer new damage. Fourth, when spring comes and the temperature reaches 10°C to 15°C, if a few plants are found to have green branches that have wrinkled, withered and died, those branches can be appropriately cut back, and fresh, loose potting soil can be replaced for planting. Fifth, because this batch of whiteorchidflowers has already suffered a certain degree of damage, after they are taken out of the greenhouse in spring they still need less watering and more misting, and only after they send out new branches and new leaves can normal water and fertilizer management be given.