1) Too much watering and long-term over-wetting of the basin soil will lead to the lack of oxygen in the soil, which will cause some fibrous roots to rot, hinder normal breathing and absorption of water and nutrients, and make the leaves turn yellow and fall off. After injury, the young leaves first turn pale yellow, and then the old leaves gradually turn yellow. Water should be controlled immediately, fertilization should be suspended, and soil should be loosened frequently to make the soil well ventilated. (2) Drought dehydration. Leakage of flowers or long-term watering (that is, wet on the top and dry on the bottom) will affect nutrient absorption, and it is also easy to cause dull and drooping leaves. First, the lower old leaves are aging and gradually wither and fall off from bottom to top. At this time, a small amount of water and water should be sprayed to make it gradually recover before turning to normal watering. (3) Long-term fertilization. Long-term non-application of ammonia fertilizer or changing pots and soil, the soil lacks nutrients such as nitrogen, which leads to sparse branches and leaves, thinning and yellowing. It is necessary to pour the pots in time, replace them with new loose and fertile culture soil, and gradually apply dilute and decomposed liquid fertilizer or compound flower fertilizer. (4) Overfertilization. If too much fertilizer is applied, new leaves will be thick and uneven, and old leaves will fall off in brown. Therefore, fertilization should be stopped immediately, and the amount of water should be increased to make the fertilizer flow out from the drainage hole at the bottom of the basin, or the basin should be emptied immediately, and the clods should be washed with water, and then replanted in the basin. (5) hot and high temperature. In summer, if the cool flowers (such as cyclamen, upside-down golden bell and begonia) are placed in a high temperature place and directly exposed to strong light, it is easy to cause the tips and edges of young leaves to burn or the leaves to fall off. It needs to be moved to a well-ventilated shade in time. (6) excessive shading. If the sunshine-loving flowers are placed in a cool place or a place with insufficient light for a long time, the branches and leaves will grow white, the leaves will become thin and yellow, and they will not bloom or rarely bloom. Be careful to move the flowerpot to a sunny place. (7) Soil and water are alkaline. The soil and water in most parts of the north contain more saline and alkali. When planting flowers that like acidic soil, such as azalea, camellia, smiling face, gardenia, orchid, magnolia, osmanthus, etc. Due to the lack of soluble iron and other elements that can be absorbed by the soil, the leaves will gradually turn yellow. Acidic soil should be used when planting, and alum fertilizer should be poured frequently during the growth period. (8) Dense ventilation. Excessive application of nitrogen fertilizer, lush growth of branches and leaves, long-term non-pruning, insufficient illumination of branches and leaves in the inner room, easy to cause leaves to yellow and fall off. Fertilization should be reasonable, and pruning should be strengthened to make it ventilated and transparent. (9) air drying. When the indoor air is too dry, some flowers that like humid environment, such as chlorophytum and orchid, often have the phenomenon of dry tip or scorched leaf edge. Attention should be paid to methods such as sprinkling water and covering with plastic film to increase air humidity, and (10) temperature is improper. When the room temperature is too low in winter, flowers that like high temperature are often vulnerable to cold damage, leading to yellowing of leaves, and in severe cases, they will die of yellowing. If the room temperature is too high, the transpiration of plants will be too strong, the water and nutrients in roots will be in short supply, and the leaves will turn yellow. Please pay attention to adjust the room temperature in time. (1 1) The soil is slightly acidic. The red loam in the south is acidic, and magnesium is easy to lose. Flowers and trees planted with alkali-resistant or slightly sealed soil, such as oleander, boxwood, Yingchun, etc., are often easy to turn green and yellow between the veins of old leaves. Calcium magnesium phosphate or magnesium sulfate solution can be applied. (12) pests and diseases. Leaf spot caused by fungi and other pathogens is easy to cause local necrosis of leaves and yellow spots or plaques. In severe cases, the leaves are completely yellow and fall off, and yellow-green mosaic spots appear after the leaves are infected by mosaic virus. Suffer from scale insects, red spiders, etc. The leaves will also become partially yellow and withered, or even the whole leaves will turn yellow and fall off. All should be sprayed in time to prevent and control. (13) Strong sexual stimulation. Too high concentration of pesticides used in pest control, or toxic gas pollution in the atmosphere, or sudden pouring of cold water when the temperature is high, are easy to cause local yellowing, burning and even death of the whole plant. Therefore, we should pay attention to the rational use of pesticides and try to eliminate air pollution sources. Avoid watering flowers with cold water around noon in midsummer. Finally, the yellow leaves of potted flowers are sometimes caused by one reason, but often by many factors. Correct diagnosis can prescribe the right medicine.