How Can Bonsai Be Grown Without Changing the Soil? A Practical Method Explained

Bonsai not only needs to be well made, but also requires good follow-up care and management. Traditionally speaking, bonsai plants usually need a soil change after being grown for 2-3 years or 4-5 years, because after a plant has been grown for a long time, the potting soil will become compacted to varying degrees, affecting the application and absorption of water and fertilizer, not only causing a waste of nutrients but also affecting the plant's growth. And repotting is often a time-consuming and laborious task that also causes some harm to the plant's normal growth. So, how can bonsai be grown without changing the soil?

In order to achieve the effect of a soil change without actually changing the soil, many people have made a series of attempts and explorations. After all, changing the soil is rather troublesome, and if the plant's growth problems can be solved without changing the soil, so much the better. Below, the editor shares the experience of a bonsai enthusiast who grows an old Buddhist pine (Podocarpus macrophyllus) in a pot without changing the soil.

I recall that a bonsai enthusiast once used an old celadon ceramic pot to grow a Buddhist pine, and normally did not fuss over it much - generally just watering it thoroughly in time when the potting soil became dry, and applying a dilute compound fertilizer once per season in spring, summer and autumn, with the concentration kept below 2%. Not only was the soil not changed for a long time, it was never changed at all. Only due to special circumstances, the old pine was moved together with its soil from the original pot into another pot one size larger, also a celadon ceramic pot. Several decades have passed since then, the soil has never been changed, and the old pine is growing well.

The above case shows that bonsai plants can indeed maintain good growth without a soil change. So this further strengthens our confidence and determination that we can grow bonsai well without changing the soil. In order to withstand the test of time and of bonsai growing results, the editor has also reached the following conclusions through practice.

If you want the potting soil to remain unchanged for decades or even forever while ensuring the plant maintains good growth, the key lies in whether there is enough space in the pot for the plant to maintain normal growth, and whether the plant's metabolic functions can still proceed normally. Whether the space in the pot is sufficient mainly depends on whether there are enough voids in the potting soil for the plant to grow.

The voids in the potting soil are mainly determined by two aspects: one is that the soil composition contains sufficient substrate particles that are difficult to dissolve in water over the long term, which is also the most basic condition for forming voids in the potting soil; the other is the "waste" produced by the root system during metabolism, which, compared with the former, is of course a secondary factor. As long as these two problems are solved, air, water and fertilizer can all be stored normally and flow smoothly within the pot, thus ensuring the normal growth activities of the bonsai plant.

It can be seen that if bonsai is to be grown without changing the soil, the preparation of the potting soil is very strict and important; the original soil must be non-sticky and heavy, poorly soluble in water, and well aerated. We can use pure coal cinders, because they have low stickiness and are difficult to dissolve in water, which is crucial for forming voids in the potting soil over the long term; moreover, coal cinders are also rich in various mineral elements and can provide the plant with a large amount of trace elements, which is very beneficial for keeping the bonsai plant growing normally.

After choosing the substrate, the method of operation is also rather important. First, crush the coal cinders into granules, remove the powder, then sift them into 2 sizes of granules. One size is about 2 cm, and the other is 1.5 cm and below; set them aside separately for later use.

When potting, place broken tiles or large gravel at the bottom of the pot to form a drainage layer, then spread a layer of coal cinder granules about 2 cm in size; finally plant the bonsai, and at the same time cover the base of the plant with the granules 1.5 cm and below, and preferably cover that with slightly larger granules of about 2 cm as the surface soil. But the soil should not be filled too full; keep some space between the soil surface and the rim of the pot to facilitate later watering and fertilizing.

For the later daily management, we can follow the usual bonsai care and management methods. But here the editor has a few points to note that everyone should understand:

1. When watering, water thoroughly, and adhere to the principle of "water when dry, not when wet; if not dry, do not water"; when fertilizing, adhere to the principle of "light fertilizer, applied frequently", and you can apply it once a month in spring, summer and autumn, usually by diluting compound fertilizer with water and watering it on, with the concentration kept below 2%.

2. Make sure the drainage hole at the bottom of the pot stays clear for the long term; in particular, avoid the bonsai plant's roots blocking the drainage hole, so it needs to be cleared at any time.

3. Because the bonsai plant keeps growing, the original pot may no longer meet its growth needs, so we need to repot it at the right time to ensure there is enough space for the plant to grow and extend, but the soil need not be changed - just use the original soil directly. However, the drainage layer still needs to be prepared in advance, and the procedure is much the same as the earlier potting.