Reasons Why Potted Flower Leaves Turn Yellow Easily and How to Care for Them
Because potted flowers have less soil in the pot and limited space, their roots cannot freely extend downward and outward, so their development is restricted. If daily management is poor and care is improper, leaf yellowing will occur more easily than in flowers grown in open ground. In mild cases, the plant's appearance is diminished; in severe cases, the entire plant dies. The causes, symptom manifestations and remedial measures are described below:
1. Water yellowing: Overwatering, with water accumulating in the pot and the soil staying wet for a long time, causes a lack of oxygen in the soil, leading to rot of some fibrous roots, which weakens the ability to absorb water and nutrients, causing young leaves to turn pale yellow and the leaves to gradually turn dark yellow one after another. Once discovered, watering should be controlled immediately, fertilizing stopped, and the soil should be loosened frequently so that the potting soil is well aerated. In severe cases, the entire root ball needs to be taken out of the pot and placed in a pile of dry soil so that moisture quickly seeps out; after the drooping branches and leaves recover, replant it in the pot.
2. Drought yellowing: Watering too little, or watering only the surface or missing waterings for a long time, causes leaf transpiration to exceed absorption, resulting in water supply falling short of demand, which can also cause leaves to turn yellow. "Drought yellowing" starts from the lower leaves, which gradually turn yellow, wither and fall from the bottom upward; in severe cases, the leaf stalks droop and appear wilted. Once discovered, the pot must immediately be moved to a shady place, some water sprayed on the leaf surfaces, and a small amount of water poured. Afterward, as the stems and leaves gradually regain their upright posture, gradually increase the amount of watering. If too much water is suddenly given at this point, it may cause plasmolysis, damage the protoplasm, and cause the flower to die.
3. Fertilizer yellowing: Applying too much fertilizer, especially too much nitrogen fertilizer while lacking phosphorus and potassium fertilizer, easily causes leaves to turn yellow. It shows as new leaves being thick and fleshy, with most leaf surfaces uneven, old leaves gradually turning yellow and falling off, and in severe cases leaf tips drying up, or even entire leaves scorching yellow. In this situation, fertilizing should be stopped immediately, watering increased so the fertilizer flows out through the drainage holes, or the pot should be turned out immediately, part of the old soil removed, the root ball washed with water, some new potting soil replaced, and the plant replanted in the pot.
4. Starvation yellowing: Insufficient fertilizing, especially when nitrogen fertilizer has not been applied for a long time or the potting soil has not been changed, leads to a lack of nitrogen nutrition in the soil, causing branches and leaves to be thin and weak and leaves to be thin and yellow. The pot should be turned out promptly, the plant removed, and it should be replanted in a pot one size larger with new loose, fertile potting soil. After watering thoroughly, place it in half-light to let it recover. After it resumes growth, apply dilute liquid fertilizer or compound chemical fertilizer.
5. Alkaline yellowing: When acid-loving flowers such as camellia, orchid, banana shrub, gardenia and osmanthus are grown in the north, because most northern regions have soil with relatively high salt and alkali content, the above plants gradually lose green and turn yellow after being cultivated for some time due to a lack of soluble iron that the flowers can absorb. At this time, apply 0.2% ferrous sulfate solution at intervals, and alternately apply 0.1% potassium dihydrogen phosphate solution, so that "alkaline yellowing" can be cured. At the same time, potassium dihydrogen phosphate also contains phosphorus and potassium, which helps flower bud differentiation and improves flower quality.
6. Acid yellowing: Southern China has red soil, and the soil is acidic or slightly acidic. Magnesium in the soil is easily lost, and due to magnesium deficiency the leaves often show yellowing first between the veins of old leaves. Calcium magnesium phosphate fertilizer can be applied; plants such as lucky bamboo will be harmed, causing leaves to turn yellow and fall off; if the room temperature is below 5°C, most flowers that like warmth and fear cold will also be harmed, with leaves, flowers and fruits turning yellow, drying up and falling off easily. Therefore, after bringing them indoors, according to the situation, spray a 0.1% to 0.3% magnesium sulfate solution. For improving acidic soil, attention should be paid to applying more decomposed organic fertilizer and applying lime. Applying a small amount of lime can not only neutralize soil acidity, but also promote the decomposition of organic fertilizer.
7. Sunburn yellowing: In summer, placing flowers that like semi-shade and fear high temperatures and intense heat, such as asparagus fern, spider plant, clivia, cyclamen and fuchsia, in a place with direct strong light for care very easily causes young leaf buds or leaf edges to scorch, or entire leaves to turn yellow. Once discovered, they must immediately be moved to a cool place with good ventilation for cultivation.
8. Shade yellowing: If light-loving flowers are kept for a long time indoors in a place with insufficient light, their growth weakens, leaves become thin and yellow, and they do not bloom or bloom very little. When growing such flowers, they usually need to be placed outdoors in a sunny or semi-lit place, and moved indoors for viewing only after they bloom.
9. Dry yellowing: In northern winters, because heating or coal fires are used, indoor air becomes dry. Some flowers that like humid air, such as orchids and Monstera deliciosa, under such environmental conditions easily develop dry leaf tips or scorched leaf edges, scorched spots on the leaves, and curled edges. Warm water close to room temperature should often be used to spray and wash the branches and leaves, and a basin of clean water should be placed on the radiator or stove to help increase indoor air humidity. For some precious flowers, it is best to cover them with plastic film at night, and place a basin of clean water inside the cover; local scorching of the leaves, or even death of the whole plant, may occur. Therefore, attention should be paid to rational application of pesticides, trying to eliminate air pollution and avoid soil toxicity.
In addition, for overly luxuriant growth, spraying pesticide is likely to cause pesticide damage, causing leaves to wither and turn yellow; contamination by toxic gases in the air or poisoning by toxic substances in the soil can also easily cause this.
Finally, it should be pointed out that the mechanism of potted flower leaves turning yellow is relatively complex. Sometimes it is caused by one reason, and sometimes by several reasons. Therefore, when yellowing leaves are found, careful observation and treatment suited to the cause are needed to achieve good results. At the same time, note that not all yellow leaf phenomena are pathological diseases. For example, when the "autumn wind sweeps away fallen leaves," deciduous flowering trees and shrubs turn yellow and shed their leaves; annual herbaceous flowers wither and turn yellow and die; the aboveground branches and leaves of perennial flowers wither; when flowers are transplanted, due to temporary nutritional imbalance, a small amount of yellow leaves fall off; and in some flowers, such as when lush branches and leaves are not pruned for a long time, causing insufficient light in the inner branches, leaves also easily turn yellow and fall off. Attention should be paid to timely pruning to make them well ventilated and well lit, and at the same time attention should be paid to appropriately applying more phosphorus and potassium fertilizer to prevent excessive growth of branches, and place a basin of clean water inside.
10. Cold yellowing: In northern winters the weather is cold. If the room temperature at this time is below 8°C, some flowers that like high temperatures, such as poinsettia, croton, bougainvillea, Calathea peacock and all kinds of variegated flowers, have temperature requirements; adjust the indoor temperature.
11. Pest and disease yellowing: When flowers are infected by pathogens such as fungi and viruses, various leaf spot diseases are caused, causing local tissue necrosis of the leaves, appearing as chlorotic yellow spots or yellow-green mottled patches, or the entire leaf turning yellow and falling off. When harmed by pests such as red spiders and scale insects, chlorophyll is destroyed, which also causes yellow-white small spots to appear on the leaves, or the leaf color to turn yellow and fall off. Once discovered, pesticide must be sprayed promptly for control.
12. Poison yellowing: When using pesticides to control flower pests and diseases, if the concentration is too high, or in midsummer when old leaves of hibiscus, white orchid and the like turn yellow after new branches sprout, these are normal physiological phenomena and not pathological diseases. (Source: Nongbo Net)