How to Fertilize Bonsai Plants? Detailed Explanation of the Correct Methods and Techniques

Bonsai have less soil, and nutrients are limited, so they must be replenished constantly; otherwise, branches become weak, leaves turn yellow, flowers are sparse, and fruit is scarce, affecting the ornamental effect. At the same time, the growth of bonsai plants must be suppressed, and generally they do not need too much fertilizer; applying too much easily makes branches and leaves grow too densely, affecting the shape. So how should bonsai plants be fertilized?

I. Types of Fertilizer

1. Organic fertilizers

These mainly include human excrement and urine, barnyard manure, poultry manure, green manure, bone meal, plant ash, soybean cake, sesame paste residue, and so on, as well as discarded organic matter from daily life such as fishy water and rice-washing water. Organic fertilizers have a wide range of sources and low cost, and the nutrients they contain are comprehensive, making them the main fertilizer for bonsai plants. Organic fertilizers must be fermented and decomposed before application; otherwise, they will ferment and release heat after fertilization, burning the plant roots.

2. Inorganic fertilizers

These mainly refer to various artificially synthesized chemical fertilizers. Commonly used ones include urea, ammonium sulfate, monopotassium phosphate, superphosphate, ferrous sulfate, and so on. Applying chemical fertilizers is relatively clean and hygienic, and for bonsai placed indoors, topdressing with chemical fertilizers should be the main approach. The nutrient elements contained in chemical fertilizers are relatively specific; when a plant urgently needs a certain nutrient element or shows symptoms of deficiency, applying the corresponding chemical fertilizer is more effective than applying organic fertilizer.

II. Fertilization Methods

1. Base fertilizer

Fertilizer applied into the potting soil when potting or repotting is called base fertilizer. The fertilizer used as base fertilizer is generally decomposed solid organic fertilizer, commonly including compost soil, bone meal, decomposed cake fertilizer, and so on. When applying it, simply mix it into the potting soil as a component of the potting soil. The fertilizer effect of base fertilizer is slow, but it lasts a long time and can provide long-term nutrient supply to the plant.

2. Topdressing

Fertilizer applied during the plant's growing period to supplement the insufficient nutrients in the potting soil is called topdressing. Topdressing can be further divided into soil topdressing and foliar topdressing.

Soil topdressing. Generally, decomposed organic fertilizer liquid is diluted with water and then applied into the pot. When applying organic fertilizer liquid as topdressing, the principle of “light fertilizer applied frequently” should be followed, and the fertilizer liquid is generally diluted 15-20 times before use. For indoor bonsai topdressing, chemical fertilizers are preferable.

Foliar topdressing. This means spraying a chemical fertilizer solution on the leaf surface; its advantages are fast fertilizer effect and a small amount of fertilizer used. For flowering and fruiting bonsai, spraying 0.2% monopotassium phosphate before flowering can promote flowering and increase the fruit-setting rate. When plants show nutrient deficiency symptoms, the foliar topdressing method can also be used for rescue treatment. Foliar topdressing is best applied before 10 a.m. and after 4 p.m., and the fertilizer concentration must be strictly controlled to avoid fertilizer damage.

III. The Relationship Between Fertilization and Plant Types and Plant Growth and Development Stages

Generally, foliage plants are fertilized mainly with nitrogen fertilizer, and the amount applied should be based on the principle of not stimulating excessive growth; flowering and fruiting bonsai have a greater fertilizer requirement and should be given more phosphorus fertilizer. Plants that prefer acidic soil should be appropriately given “alum fertilizer water”; “alum fertilizer water” is made by adding about 1% ferrous sulfate when preparing organic liquid fertilizer, then using it after fermentation and decomposition.

Different stages of plant growth and development have different nutrient requirements. Generally, in late spring and summer, plants enter a period of vigorous growth and should be fertilized more; after autumn begins, the growth rate slows down, so less fertilizer should be applied to avoid excessive growth; in winter, most plants enter dormancy and fertilization should be stopped. Flowering and fruiting bonsai should be given more phosphorus fertilizer during the flower bud differentiation stage and before and after flowering.

The above is an introduction to the fertilization methods for bonsai plants. Friends who grow bonsai plants can refer to the above fertilization methods and fertilize reasonably according to actual growing conditions.