A Detailed Guide to the Latest Fertilization Methods for Pine Bonsai

In the wild, pines mostly grow in barren or high-altitude areas and are pioneer tree species that are heliophilous (sun-loving); that is, pines do not need much fertilizer to grow well. In horticultural cultivation, to make trees grow quickly and shorten the cultivation time, fertilizer is still applied, especially by us amateur growers, who spare no fertilizer and wish the tree could grow an inch overnight.

Because bonsai are cultivated in the limited space of a pot and within the planting soil, organic matter is decomposed by bacteria into inorganic salts and absorbed by the tree roots. As the pine grows and consumes nutrients, the necessary nutrients in the pot gradually decrease, leading to insufficient nutrition and making growth difficult, so nutrients must be replenished regularly. Fertilization must grasp the quality and quantity of fertilizer used during the pine's growth period and storage period in order to fully bring out the fertilizer's efficacy and meet the pine's growth needs.

Fertilization should vary according to the different tree species, the age of the tree, the size of the pot surface, and the different quality and nature of the fertilizer. Fertilization must be determined according to the characteristics of root growth, distribution, and absorption to decide which fertilizer to apply. Generally speaking, more fertilizer should be applied during the growth period and the nutrient accumulation period, and less fertilizer should be applied to finished trees and during the dormant period.

Basic principles of fertilization:

The organic fertilizer used must be fully decomposed; raw fertilizer that has not been fermented and decomposed cannot be used. Raw fertilizer that has not been fermented can harm the pine's roots and affect the surrounding environment. Whether applying organic fertilizer or inorganic fertilizer, apply less but more frequently. Fertilization must be timely; if the leaf color becomes pale and growth becomes weak and thin, nitrogen fertilizer should be applied immediately. Fertilization should take temperature into account; when the temperature exceeds 25°C, fertilizer should not be applied.

Fertilizer can be divided into natural organic fertilizer and chemically synthesized inorganic fertilizer. Inorganic fertilizer has a high concentration and stable composition; long-term use of inorganic fertilizer easily makes the potting soil acidic or alkaline, hindering the pine's growth. The organic fertilizer used must be fully fermented before use. Dilute the original liquid with 10 times the amount of water, then pour it into the potting soil. Those who dislike the smell can add sulfurous acid before watering; besides having a deodorizing effect, it can increase the green color of the leaves and reduce melanin.

1. Spring fertilization:

For trees with weak vigor, fertilizer can be applied a little earlier, around 2 to 3 months after the buds begin to move. Since the tree is weak, it is not possible and not necessary to apply too much fertilizer at one time. Pine bonsai are repotted from February to March each year, and fertilization begins in May, applied once every 15 days for three consecutive times, because this is exactly the pine's growth period. By mid-June, fertilization stops, because the temperature is relatively high at this time and fertilizing easily damages the roots. Pine bonsai should be given more phosphorus and potassium fertilizer and less nitrogen fertilizer.

2. Autumn fertilization:

In late summer and early autumn, around August to September, when the weather begins to turn cooler and the pine starts rapid growth again after its summer dormancy. Generally speaking, autumn fertilizer must be applied; if fertilizer is not absorbed sufficiently in autumn, new shoot growth will be poor the following spring, affecting the growth vigor for the whole year.

In summer, when the temperature is too high and sunlight is strong, and in winter, when the temperature is low and sunlight is weak, pine growth slows down (cells grown in summer are the same size as, or even larger than, those grown in spring and autumn; from the annual rings, the phenomenon of slow summer growth cannot be seen), so (too much) fertilizer is not needed, especially under full sun in summer, when water evaporates quickly. If too much fertilizer remains in the potting soil, the ion (fertilizer) concentration in the water may rise greatly due to water evaporation, causing fertilizer burn; even if it does not reach the level of fertilizer burn, it will, through osmotic pressure, reduce the plant's ability to absorb water, diminishing the effect of the pine's particular need to rely on transpiration to cool down when the temperature is high.

After repotting, it is best to wait 1 to 2 months before fertilizing; if the timing is missed, wait until the next time. Missing one fertilization is not a big deal (if the pot was only lifted without removing the soil, fertilization can be done one week later in coordination with the spring and autumn fertilization timing, but it should not be excessive, as that would affect the extension of new roots).

Fertilization begins in early October each year, applied once every 15 days for two consecutive times, with more phosphorus and potassium fertilizer, in order to accumulate nutrients. Fertilization should note:

(1) The pot surface should not be too dry, because fertilizing when it is too dry easily damages the roots, nor should it be too wet, because when it is too wet the tree roots cannot absorb the fertilizer and root rot easily occurs.

(2) Fertilization should be done less but more frequently, and the potting soil should be neither dry nor wet, which is most suitable. Nitrogen fertilizer is an important element that makes up proteins. If nitrogen fertilizer is insufficient, the leaf surface becomes pale and growth declines; if there is too much nitrogen fertilizer, the stems and leaves become weak. The main function of nitrogen fertilizer is as a leaf fertilizer.

(3) Phosphorus fertilizer can form cells and has a great influence on cell division. It works together with nitrogen and potassium to exert its greatest effect. Insufficient phosphorus causes poor root development. Phosphorus fertilizer is mainly based on bone meal, and phosphorus fertilizer has the effect of promoting flowering and fruiting.

(4) Potassium fertilizer has a great influence on photosynthesis and can help transport nutrients to the roots and branches, enabling their extension and activity. Potassium can adjust potting soil that is too acidic, and plant ash can also be used to correct acidity in the soil. Potassium fertilizer has the effect of strengthening the roots, promoting the bonsai tree's absorption of nitrogen and phosphorus, and making it strong and resistant to cold and heat.