Causes and Control Methods of Leaf Yellowing in Winter Red Fruit Bonsai

Winter red fruit flowers easily and has a high fruit-setting rate. Its fruits are entirely red, and the fruiting period can extend to the next year's flowering and leafing stage without dropping. It is an excellent variety for fruit-viewing bonsai and is deeply loved by the people. However, during cultivation, due to the limitation of pot capacity and other influences, the leaves often turn yellow and drop. The main causes of yellowing are as follows:

Temperature

Winter red fruit prefers warm and humid conditions and likes light but not excessively strong light. Especially in hot summers, strong direct sunlight will make the air dry and raise the pot soil temperature, causing damage to the root system, reducing enzyme activity, and causing the leaves to turn red, with leaf tips drying up, yellowing, and dropping. Therefore, in summer, it should be placed in a ventilated place, and water should often be sprayed around the tree body to lower the air temperature.

Light. Strong light tends to cause yellowing, wilting, and scorched shoot tips of branches and leaves, while weak light tends to cause leggy branches, poor fruit coloring, and small yellowing leaves that drop. Therefore, when winter red fruit enters the ornamental period, its indoor placement should be close to a windowsill so that it is under bright scattered light.

Water

① Excessive watering of the pot soil causes waterlogging, making the pot soil lack oxygen. Some fibrous roots suffocate and rot, losing the ability to absorb water and nutrients. At the same time, respiration increases bicarbonate ions (HCO3), which further affects iron absorption, causing the top young leaves to become pale yellow and wilted, while the old leaves gradually turn dark yellow. If this phenomenon is found, the plant should immediately be removed from the pot with its soil ball, placed in a cool and ventilated place, and water should often be sprayed on the leaves. Do not spray water on the roots anymore, so that the water can evaporate as quickly as possible. After the plant returns to normal, repot it.

② If the pot soil is not watered for a long time or watering does not penetrate thoroughly, winter red fruit will show normal color in the top center and new leaves, while the lower old leaves gradually dry yellow upward, curl, and drop, and the fruits shrivel, with serious fruit drop. When this happens, do not immediately water the pot soil thoroughly. First place it in half shade, spray water on the leaves first, and when the leaves are no longer wilted, use the soaking method to let the pot soil slowly absorb water thoroughly. If watering is used, because the pot wall cracks are loose, water easily escapes from the gaps, resulting in incomplete watering. In short, follow the principle of "do not water when dry, and water thoroughly when watering."

③ Winter red fruit prefers slightly acidic soil. Because water in the north is rather alkaline, long-term watering causes the pot soil to gradually become alkaline, so the plant cannot absorb iron. During cultivation, often use 1 part ferrous sulfate, 10 parts soybean cake fertilizer, and 200 parts water, and after decomposition, dilute it before use to change the alkalinity of the pot soil.

Fertilizer

① Excessive or too concentrated fertilization causes yellow leaves. It appears as new leaves that are thick and glossy with a dark green color, but the leaf backs are shrunken and raised, the leaves are not smooth and spreading, and the lower old leaves of the plant gradually turn yellow and drop. At this time, winter red fruit should be placed in shade, and the flower pot should be soaked in water to dilute the fertilizer. After two hours, remove the plant from the pot with its soil ball and dry the moisture. If necessary, remove the old leaves and remove part of the old soil to replace it with new soil.

② Winter red fruit grows vigorously and needs repotting once every 2 to 3 years; otherwise, a root mat easily forms, resulting in poor pot soil aeration, difficulty for the root system to absorb water and fertilizer, thin and weak branches, long internodes, thin, tender, yellow leaves, poor flower color, and difficulty setting fruit. Therefore, during the dormant period, repotting and soil replacement should be carried out together with root pruning.

③ During cultivation, because undecomposed organic fertilizer is applied, the fertilizer ferments in the pot, burning or poisoning the root system. The root system turns black and rots, the leaves wilt and turn yellow, and even the whole plant dies. Therefore, organic fertilizer must be fully decomposed before use.

Difference between iron deficiency and manganese deficiency: The degree of chlorosis in iron deficiency is usually deeper, the boundary between yellow and green is usually obvious, and brown spots generally do not appear, while the degree of chlorosis in manganese deficiency is lighter, and brown spots or brown streaks often occur.