Causes of Leaf Drop in Bonsai Ficus in Northern Cultivation and Preventive Measures

Ficus (Ficus microcarpa L.) is an evergreen ornamental plant of the Moraceae family, generally grown as bonsai in the north. Its leaves are bright green, its branches and trunk are vigorous and rugged, and its forms are endlessly varied; the coiled and twisting aerial roots in particular give a sense of antiquity, desolation and richness. It is an excellent bonsai plant. However, bonsai ficus grown in the north always drops its leaves, seriously affecting its ornamental effect. The author has investigated this for many years, analyzed the causes, and summarized preventive methods.

1 Causes of leaf drop

Leaf drop of bonsai ficus in the north can be divided into two situations.

1.1 Leaf drop in a healthy ficus just purchased is mainly induced by a sudden change in the growing environment. Temperature, humidity and light, especially a sharp change in environmental humidity, will directly cause the ficus leaves to fall in large numbers within a short time.

1.2 For bonsai kept for a long time, leaf drop should be considered in relation to factors such as gradual weakening of tree vigor, insufficient nutrition, lack of fertilizer in the soil, alkalization, or pests and diseases.

2 Measures to prevent leaf drop

2.1 When purchasing, choose a healthy plant with spreading leaves, deep green and glossy color, and no pests or diseases on the whole plant, and preferably one that has been grown in a pot for a long time. This can be judged by whether there are traces of recent digging on the surface of the potting soil. The growing medium should be loose, fertile and air-permeable.

2.2 After purchase, strengthen management and pay attention to imitating the previous growing environment; especially at the very beginning, pay attention to increasing the air humidity around the ficus plant so that it gradually adapts to the new environment.

2.3 Daily management: normally place it in a relatively bright indoor location, with winter temperatures not below 5°C and summer temperatures not above 35°C, and pay attention to ventilation, frequently spraying water on the leaf surface. During the period after Grain Rain and before Cold Dew, it can also be placed outdoors for cultivation, with slight shading in midsummer. Note that in a dry indoor environment it should be kept away from heat sources, especially at low temperatures.

2.4 Fertilization: pay attention to frequent light fertilization, and apply more dilute fermented cake fertilizer water or alum fertilizer water. You can also occasionally spray 0.2% urea water or 0.2% potassium dihydrogen phosphate solution, etc., but be sure to avoid concentrated fertilizer and raw fertilizer.

2.5 Actively prevent and control pests and diseases. Although leaf pests and diseases can cause leaf drop, root pests and diseases can also cause leaf drop. Pay attention to careful observation, analyze the causes, and prevent and control them early and promptly.

2.6 Application of plant growth regulators: appropriate application of plant growth regulators to regulate growth can prevent leaf drop. When fertilizer and water are sufficient and during the vigorous growth periods in spring and autumn, retardants such as paclobutrazol and chlormequat can be sprayed to control growth and strengthen tree vigor. Once the ficus drops its leaves, anti-drop agents, cytokinins, etc. can be sprayed. The specific types and concentrations to apply should be determined according to the specific situation. At the same time, soil, fertilizer, water and management should also be considered comprehensively, and treatment should be applied according to the cause.